CN1105296C - On-line quantitative analysis of chemical compositions by raman sepectrometry - Google Patents

Abstract

The present invention relates to a method for quantitatively monitoring not less than one component selected from chemical compositions in fields by Raman spectrometry. The method comprises: a reference material and a chemical composition containing not less than one component are simultaneously irradiated with a fundamentally monochromatic radiation source, and radiation rays are transmitted to the chemical composition through an excitation guide pipe, namely that the excitation guide pipe connects the radiation source to an optical probe in junction with the composition; meanwhile, the convolution Raman spectrum of the reference material and the chemical composition is collected by means of a spectrometer at a place with more than one wavelengths, and the spectrometer is connected with the optical probe through a collection guide pipe; the standard Raman spectrum of the reference material is selected; the convolution function of the convolution spectrum obtained from the convolution Raman spectrum and the standard Raman spectrum of the reference material is measured; the convolution Raman spectrum of the composition is regulated by applying the convolution function in order to generate the standard Raman spectrum of the chemical composition; a correction method measured in advance is used for the standard Raman spectrum of the chemical composition. In this way, the chemical composition of the composition in the sampling of the convolution Raman spectrum can be measured.

Description

The method of the component of Quantitative Monitoring Chemical composition that

FIELD OF THE INVENTION

The present invention relates to Raman spectrum analysis, more specifically relate to a kind of method with Raman spectrum in situ quantitation ground monitoring Chemical composition that component.

Background of the present invention

Physics and the analytical property of measuring material with spectrum in the assay laboratory are a kind of proven technique.Raman spectrum is a kind of in this class technology, and it can provide the information of the qualitative and quantitative aspect of the composition of relevant chemical substance and/or molecular structure.A kind of process that is called scattering can take place in it when incident radiation and matter interaction.Ray through scattering can be flexible, and at this moment the wavelength of incident ray does not change in scattered radiation, can be stiff yet, and wherein the wavelength of scattered radiation is different with incident radiation.In inelastically scattered a kind of form, claim that it is Raman scattering, the photon of incident is when scattering or obtain energy, perhaps degradedness.The difference of scattering and incident radiation energy is commonly referred to as the Raman migration.The Raman that obtains migration spectrum provides the energy message of various molecular vibrations motions and has passed on about the chemistry of the material studied and the message of molecular structure aspect.Raman scattering effect is extremely weak; Typically, in millions of elastic scattered photons, only there are several Raman scattering photons.

Measuring the composition of Chemical composition that or the progression of monitoring chemical reaction usually implements with the material that is in the severe rugged environment.Often need in analysis process materials flow under high temperature and/or the condition of high voltage or under the condition that exists of be corrosive material or strong solvent.For example, may require to follow the tracks of the reaction that a reactant by lower molecular weight forms polymkeric substance, this reaction is at high temperature continuous or batch (-type) ground carries out.Similarly, also may want to monitor one in the batch reaction composition or be in the time dependent function of volatile material of distillation cat head.Spectrophotometric instrument such as spectrograph and radiation source can be installed in away from the material of wanting on-the site analysis such as the composition that forms polymkeric substance and the place of distillating mixture.The sampling location can be connected on the instrument by the radiation catheter that contains optical fiber.

Certainly, method of the present invention is not only to be limited to be used in and is it is characterized by, for example, and the severe rugged environment of higher temperature.According to the present invention, quantitative on-the-spot raman spectroscopy measurement can be implemented in various environment, comprises in the organism alive, as long as can obtain suitable optic probe.

Polyester is a kind of synthetic resin, comprises the ester connecting key in its main polymeric chain.The polyesters that commodity value is arranged as aspects such as cloth fibers, container packages is made by various reactants.For example, the ester exchange reaction of esterification, dicarboxylic ester and the glycols that they can be by dicarboxylic acid and glycols or the self-condensation reaction of hydroxycarboxylic acid are produced.

For reaching the characteristic of the specific final request for utilization of a kind of polyester, need be in manufacture process in reaction vessel the ratio of strict control each component or the composition of material.The small variations of initial composition may have influence on the availability of final polyester product tempestuously.For guaranteeing the characteristic of reliably final polyester product, also require control ester or acid end group to be converted into the process of active hydroxyl end groups, this depends on two esters of gallic acid or omega-dicarboxylic acids.Thereby the activity that low conversion ratio has limited polycondensation reaction in first step course of reaction has negative effect to the final use character of polyester material.For this reason, know that conversion ratio or transforming degree that the first step is reacted are very important.Other critical composition controlled variable is included in the reaction vessel partly quantity of every kind of diacid and glycol, total glycols to the ratio of two total acids and/or diester class and the length of the degree of polymerization, molecular weight or polymer chain etc.

In manufacture process, the chemical composition of material can be measured in laboratory at a distance for the sample of analytical test by taking out in a small amount in the reaction vessel.The analytical approach of common use can be used to provide the indication of the aspects such as degree of the molar ratio of reactant and product in the first step extent of reaction, the potpourri and reaction.Generally be used in the laboratory method obtaining extracting sample composition information comprise nuclear magnetic resonance (NMR) spectrum, gas chromatography (GC) and liquid chromatography (LC).The sample that these methods require to be extracted can be dissolved, and in some cases can be by derivatization.The NMR method can provide reliable information; Yet required instrument is expensive and complicated, and sample must suitably be prepared before measuring.

The problem that the present invention solves

The sampling repeatedly and the analysis to measure that are used for chemical production processes have proposed some noticeable potential problems.

At first, from the production materials flow of heat, take out sample, when material is in forming polymer process during thickness, have intrinsic danger especially.Big insulation valve must be opened so that material flows in the little sampling container.Partly stopped up at polymer production line up-sampling mouth, caused that the material of heat unexpectedly neither be uncommon from the situation of opening part discharge.

Secondly, the program of taking-up sample may change the composition of sample.For example, the reaction of the first step in a kind of conventional polyester manufacture method is generally carried out with excessive ethylene glycol (EG) in reactor.EG is than the easier volatilization of oligomeric material, thereby and in may be when from process, being removed by sample preferred flash distillation cause the sample of extraction under-represented.Also have, when the material of being gathered is a thickness, it may adhere on the thief hatch valve, this will cause current adopt sample and when sampling last time the sample of remnants be blended together mutually.

The 3rd, this sampling and routine analyzer are time-consumings very, are used for gathering, prepare and analyze in time of a sample and can produce the materials of number in kip at needs.The analysis data that obtained by sample only have limited value for the process control of preceding taking the photograph.

At last, owing to take out the difficulty of sample and the expense that combines with risk, analytical sampling does not frequently carry out usually.With little quantitative analysis data point, just be difficult to obtain statistically validly carry out suitable regulating and controlling to the understanding of technological parameter or to technology.

Should in material production, monitor material through preferred analytical approach.A kind of like this method should be able to reduce from production environment the requirement of taking out sample, reduces the problem of secure context, and makes more frequent and measurement faster becomes easy.

Yet some challenging obstacles have hindered most of analytical technologies and have been provided at the scene in the production environment, online chemical composition information.At first, this analytical approach must accurately be measured required character with sufficient precision.The second, this analytical instrument must tolerate to such an extent that live the physical environment of Production Regional or must differentiate the character of required composition from afar.The 3rd, the interface of instrument and production line must be able to tolerate the firmly harsh pressure and temperature environment of chemical production line inside.The 4th, the phenomenon in dirt, bubble and other the common production must this analysis to measure of unlikely interference.All these obstacles are all overcome by method of the present invention.

Summary of the present invention

A kind of method with one or more selected components in the Raman spectrum in situ quantitation monitoring Chemical composition that, it comprises: shine a kind of reference material and the Chemical composition that contains one or more components simultaneously with the radiation source that is monochrome substantially, ray is sent to Chemical composition that to radiant rays from radiation source by exciting conduit, and this conduit connects radiation source to connecing on the optic probe on boundary with composition; Gathering the convolution Raman spectrum of reference material and Chemical composition that more than a kind of wavelength place simultaneously by spectrograph, spectrograph connects to optic probe by connecting duct; Select the standard Raman spectrum of reference material; Convolution function by the standard raman spectroscopy convolution spectrum of convolution Raman spectrum and reference material; Use the convolution function and regulate the convolution Raman spectrum of Chemical composition that to produce the standard Raman spectrum of said composition; The bearing calibration of measuring in advance is applied to the standard Raman spectrum of Chemical composition that, thereby determines the chemical composition of composition when gathering the convolution Raman spectrum.

Beneficial effect of the present invention

Method of the present invention is a kind of significant improvement to the traditional analysis method, and it can obtain more reliable measurement result in time still less, and does not have the difficulty of taking out sample continuously.The control strategy that the information that obtains can be used to design of feedback or feed-forward type is to improve production quality, to reduce waste product, to improve craft rate of production and reduce to follow when taking out sample in the chemical fabrication processes flow process and taken risks.

Brief description of the drawings

Fig. 1 is the Raman spectrum of poly-(ethylene glycol terephthalate) intermediate.

Fig. 2 is the diagram of Raman spectrum system.

Fig. 3 is for measuring the correlogram of the terminal usefulness of methyl in the composition that forms polymkeric substance.

Fig. 4 is dynamic (dynamical) figure of summing up dimethyl terephthalate (DMT) and glycol reaction.

Fig. 5 is a figure of using Raman spectrum and NMR spectroscopic analysis methods gained data in the comparison production of polyester line.

                   Detailed description of the present invention

Commercial useful chemicals for example, generally is the temperature by raising such as polyesters Made by extensive continuous processing under the condition. The arts demand of these polyesters preparations carries out ester Change the esterification of reaction such as dicarboxylic acids, or the ester exchange of dicarboxylic ester class and glycols compound Reaction.

The glycols compound contains two hydroxy functional groups. Many glycols all can be used for polyesters In the manufacturing, comprise, for example, ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol, polyethylene glycol, Polytetramethylene glycol, polypropylene glycol, poly-Isopropanediol, BDO, neopentyl glycol and 1,4-CHDM (CHDM).

Two acids contain two carboxyls partly. For the manufacture of the representational diacid in the polyester material Class comprises: terephthalic acid (TPA) (TPA), M-phthalic acid, naphthalenedicarboxylic acid, Isosorbide-5-Nitrae-cyclohexane Dioctyl phthalate (CHDA) and various aliphatic dicarboxylic acid.

The dicarboxylic ester class contains two ester functional groups. The example of useful diester class comprises just to be mentioned Any esterification derivative of two acids. Important two of a kind of common manufacturing for polyester material Ester is dimethyl terephthalate (DMT) (DMT).

Poly-(ethylene glycol terephthalate), i.e. PET is of commercial useful polyester Example. This polymer is normally made by DMT or TPA and EG, generally is divided into two In the step, exist such as OdianThe polymerization principle( Principles of Polymerization) the 97th to 100 page of the book third edition (Wiley, New York publishes, 1991) and Billmeyer existPoly- The textbook of compound science( Textbook of Polymer Science) a book third edition 442 to 445 pages, described in (Wiley, New York publish, 1984) like that. In the first step, excessive EG and DMT or TPA react, and form the intermediate terephthaldehyde Two (2-ethoxy) esters (BHET) of acid, its Raman spectrum is depicted in the accompanying drawing 1. In this technology of generally under 150-230 ℃ of temperature conditions, carrying out, depend on it is with DMT also Be TPA, have respectively methyl alcohol or water generates, and remove by distillation continuously. Claim at second step In the process for polycondensation reaction, material is heated to 270-300 ℃ temperature. Polymerisation is logical Cross and remove EG and carry out, and usually use partly the condition of vacuum (0.0133 to 0.133kPa, Suitable 0.1 to 1torr) make reaction be easy to carry out. Polymerization process has improved the molecular weight of molecule with big Little, thus many chemistry and physical property changed.

The character of polyester material can by in polymer architecture, incorporate into different glycol, diester or Two acid constituentses and modifying. For example, available CHDM replaces in the first step reaction of PET EG, forming a kind of distinct polyester, the character that it has and final use and based on EG Product entirely different. Further, people can use various glycols, diester class, two acids completely Or the formed mixture of their combination, make other polyester material with peculiar property. For example, glycols CHDM and EG can be blended in together, form a kind of with the DMT reaction PET through the ethylene glycol modification. The modified polyesters of many these classes has been described in patent documentation In, comprise United States Patent(USP) Nos. 4,259,478; 3,772,405 and 3,033,822.

Typical Raman spectrometer is device, the receipts that are sent to sample by radiation source, the source radiation Collection is from the device of the scattering radiation of sample, the energy separation of scattering radiation, or the device that disperses, And the device that detects radiation.

There are many radiation sources can from material, produce Raman scattering. Be the purpose of analysis to measure, this High-intensity monochromaticjty radiation need to be launched in a little sources. In this respect, laser instrument is very suitable radiation The source. U.S. Patent No. 3,556,659 have described a kind of Raman spectrometer, wherein are included in an examination Sample in the pipe is used for the axial irradiation along pipe from the ray of laser instrument.

Various types of lasing sources are arranged, comprising: gas laser such as helium-neon, nitrogen, argon Ion and krypton ion etc.; Solid-state laser such as ruby laser and Nd:YAG laser instrument are (namely Neodymium: the Yttrium-Aluminium-Garnet laser instrument); Dye laser; Chemical laser; And solid-state sharp The light device is such as monotype and multimodal diode laser.

In these laser instruments, gas laser generally is considered to be particularly suitable for the color dispersion-type Raman light Spectrometer is because they have the wavelength stability of height. Unfortunately they often very expensive, need Maintenance measure or only have low power output widely. In Raman spectrometer, use semiconductor Diode laser can provide big power stage in the firm device of compactness, but it may be defeated Go out to present inherent unstability in the character, these are described in Wang and McCreery,Anal. Chem.，1990, Vol, 62, the 2647-2651 pages or leaves.

Because the Raman scattering process relates to the migration of incident ray wavelength, so different laser instruments provides Be spectrum in different wavelength regions. Similar at those regional Raman migration spectrum but. And be identical structure message basically by using different laser wavelength of incidence resulting.

Fluorescence is to be absorbed the process that radiation-actuate goes out broad emission band, and its feature is relevant with molecular structure.If observation can be seen the fluorescence signal that brings out generally than the big quite a lot of orders of magnitude of Raman signal, covering Raman migration spectrum in some cases fully.Like this, preferably select the wavelength of incident ray, make its fluorescent emission process minimum.

A kind of well-known method that reduces the fluorescence background problem is to use the laser instrument that can produce redness or near infrared light, and its wavelength is about 660 nanometer to 1100 nanometers, exists as D.B.Chase J.Am. Chem.Soc.,Described in 1986, the 108 volume 7485-7488 pages or leaves.This method is useful, is the transition process that begins from the incident ray wavelength because the fluorescent emission profile is independent of the wavelength and the Raman Process of incident ray.Operate in diode laser, multimodal diode laser and Nd:YAG laser instrument that this regional typical source of radiation comprises krypton ion gas laser, monotype.

In numerous obtainable radiation sources, laser instrument is highly preferred, and this is because their powerful, the monochromaticity radiation characteristic of power.In the commercially available laser instrument of numerous types, diode laser is preferred, and this is because they only need very little maintenance measure in long useful life period.This advantage is very attractive as the parts of industrial analysis instrument.Further, highly preferredly be to use a kind of fiber optic cable laser instrument that is coupled in advance.Be called as the coiling diode laser with the diode laser apparatus of fiber optic cable coupling, can have bought from market.

The coiling diode laser has some great advantages than other lasing light emitter.At first, they with the fiber optic cable coupling, this has just eliminated complicated mechanism of optical correction, the latter may not focus on and causes dropout.This simplicity makes it take out easily when needed and replace.In addition, diode laser has long serviceable life usually, thereby only needs minimum maintenance.Also have, diode laser can be by thermal tuning in little wavelength coverage, and it provides a kind of method of offsetting any contingent slight wave length shift.At last, diode laser can be made has high power, makes to obtain more powerful signal, and the result only needs short Measuring Time.Relevant with the higher-wattage diode laser is that they can so-called " multi-mode " be operated, and at this moment many laser form patterns and all work simultaneously.These each other patterns are unsettled mutually, thereby make this device measure useless to the quantitative test of precision.The instability of diode laser can be reduced by suitable control temperature and undesirable emission but can not be eliminated fully, as people such as Carrabba at SPIE, 1991, Vol 1434 delivers " the compact Raman instrument that is used for technology and environmental monitoring; " " environment idea and combustion characteristic " is described in the 127-134 page or leaf.Do not wish the Laser emission wanted for control, people such as Carrabba have described a kind of holographic optics sideband filter, and it has very high optical density at the laser wavelength place.

Do not add control, be unsettled such as those diode lasers of describing, thereby generally be considered in raman study, there is not what use.Further, the wavelength migration can take place in any diode laser device gradually when this device is aging.A kind of diode laser apparatus, though can stablize the short time, long-term feature is unsettled, it produces the reduction that drift slowly causes instrument reliability.

Can buy from market at the diode laser of various incident ray wavelength work.Preferably use the laser instrument of wavelength between about 700 nanometers and 900 nanometers.Be lower than context process that 700 nanometers have some interference such as fluorescence, and more in vogue during than higher wavelength.But wavelength surpasses 900 nanometers then can have a negative impact to the detectability of normally used multi-channel detection system.

The inventive method in embodiment preferred, used Raman spectrometer comprises the multi-mode diode laser of a high power, coiling, its emitted laser is between about 780 nanometers and 830 nanometers.But, the method that is addressed in the present invention is not limited to this instrument.

Elastic scattering requires effective photon separation method to the big ratio of Raman scattering photon.Traditionally, this finishes with twice or No. three spectrograph systems, and they are made of two or three dispersion elements respectively.Other radiant rays filter filtering elastic scattered photons effectively is so that allow to use less, more effective single dispersion element spectrograph device; For example, holographic Bragg diffraction filter is described in people such as Carrabba and exists Appl.Spec.,In the article of 1990, the 44 volume 1558-1561 pages or leaves.

It is very important that detector element has suitable performance to Raman instrument, and it must tell extremely low intensive radiation.Traditional scanning monochromator system uses photomultiplier, and it can observe low intensive photon signal.Newer instrument uses array detector such as photodiode array (PDA) or charge-coupled device (CCD).Array detector is made up of many optical elements, and these optical elements can be observed a SPECTRAL REGION simultaneously, up to whole Raman spectrum.The CCD detecting device be multidimensional and can observe a plurality of Raman spectrums simultaneously more than a kind of wavelength place, at SPIE, 1992, the 1637 people such as volume 118-125 pages or leaves and Angel are at SPJE as people such as Vess, 1991, the 1587 volume 219-231 pages or leaves are described.

Described in the paper of above-mentioned Wang and McCreery charge-coupled device and near-infrared diode laser one have been used from the highly sensitive Raman spectrometer.Also have, people such as Newman also exist Appl.Spec.,1992, the 46 volume 262-265 pages or leaves have been described CCD and have been had the use supply of diode laser of flat field imaging spectrograph and the fiber optics interface between sample.

The Raman spectroscopy instrument that single chromatic dispersion grating spectrograph and CCD detecting device, monotype diode laser, optical fiber cable, fibre-optical probe and suitable computer structure are lumped together is useful for assay determination fast.Yet the mechanical stability of spectrograph and detection system, other optical interface and the instability of above-mentioned diode laser have limited the quantitative test ability of this instrument.Fourier Tranform (FT) Raman spectrum has been proposed for quantitative chemical analysis.Yet because the change of instrument, its reappearance also is generally limited to one of about percentage under best-case, exist as people such as Seasholtz Appl.Spee.,1989, the 43 volume 1067-1072 pages or leaves are described like that.

Traditional laboratory Raman instrument uses a series of lens, level crossing and other optical element transmits and the focusing source is radiated on the sample.Fiber optic cable progress, for example, Allred and McCreery exist Appl.Spec.,1990 the 44th volume 1229-1231 pages or leaves and Schwab and McCreery exist Anal.Chem.,1984, the 56 volume 2199-2204 pages or leaves are described, and a kind of short-cut method that guides radiant rays towards sample is provided.Fiber optic cable simplicity, dirigibility and output efficiency have been created the prospect of measuring feasibility from afar.

The quartzy core body of fiber optic cable melting though be weak Raman scattering body, can provide interfering background signal when using long fiber lengths, as in U.S. Patent No. 5,112,127; People such as Vess are at SPIE, and 1992, the 1637 roll up the 118-125 pages or leaves; People such as Schoen are at Appl.Opt., and 1992, the 36 roll up the 7707-7715 pages or leaves; People such as Schoen are at SPIE, and 1993, the 1857 roll up the such of 116-125 page or leaf discussion.Being used for overcoming this difficult basic fundamental is to use optical filter in the position near sample.These wave filters just filtered out the ray that induces background before producing interference.

Fibre-optical probe generally is to be used in combination with optical fiber, providing a kind of radiant rays that transmits to the sample and the method for collecting the scattered radiation line, as, for example, U.S. Patent No. 4,573, described in 761 like that.This class probe can be used in combination fiber optic cable, lens and/or level crossing and constitute.In a kind of formation, two strands or multiply optical fiber are placed in together tightly at the sample end.Have one or more strands of being used to that radiant rays is sent to the sample the inside in these optical fiber, one or more strands of in addition optical fiber then are used for collecting and transmit scattered ray and give detecting device.

After scattered ray was collected and transmits, it was separated with dispersion element.Dispersion element general and focusing and collimation optics in spectrograph make the disconnected from each other of various energy levels of scattered ray become easy together.Often, remove parasitic light more completely and increase resolution with two-stage or multistage dispersion element.But, have great advantage with less, more effective single grating spectrograph in conjunction with suitable optically filtering, in the paper as the Allred that mentions in front and McCreery and Wang and McCreery, also have people such as Carrabba at SPIE, it is such that 1991, the 1434 volume 127-134 pages or leaves were described.The big fes signal output of Huo Deing adds like this provides a kind of very sensitive and reproducible measuring method.

On-line analysis method based on Raman spectrum came into question in some references.For example, Garrison is at SPIE, and 1992, the 1681 volume 291-293 pages or leaves were described and used FT, the Raman system is monitored the composition in the distillation column, and wherein one little materials flow is taken out from distillation tray and entered in the cell of a temperature control.The Raman probe is inserted in this environment and comes image data; This method has about 2 percent relative accuracy.Described a kind of FT-Raman laboratory method in people's such as above-mentioned Seascholtz the paper, be used for being oil fuel product development calibration curve with limited quantitation capabilities.James people such as PCT Int.Appl.WO 87/06011 and Nguyen at French Patent (FRP) No.2, described in 571,144 for on-the-spot on-line determination compound analysis from afar learn character or chemical composition in conjunction with used Raman ray monitoring device; But do not illustrate with the accessible precision of described method.

Method of the present invention is used in particular for the field monitoring polyester production process.Known for a long time with the Raman spectrum analysis polyesters; Referring to, for example, people such as Bulkin, big molecule ( Macromolecules) 1987, the 20 volume 830-835 pages or leaves; People such as Bower, polymkeric substance ( Polymer), 1982, the 23 volumes, 645-649 page or leaf; People such as Adar, polymkeric substance ( Polymer), 1985, the 26 volumes, 1935-1943 page or leaf; And people such as DeBlase, the polymer science magazine J.Polym.Sci.,1985 the 23rd volumes, the 109-115 page or leaf.Typically, the final products polyester material is studied to determine its conformation, orientation and crystallographic property by the lab analysis of off-line.Observed violent change corresponding to the polymeric material vibrational spectrum of technology difference.Conformation, orientation and crystallinity all can influence the character of final products and to the use of concrete application facet.

A kind of typical Raman spectrum of PET monomer sample is shown among Fig. 1.This spectrum characteristics is the various peaks of some certain vibration motions in the indication molecule.For example be positioned at about 1610cm ^-1The peak at place is to open with the symmetry of terephthalate member ring systems/relaxation motion associated.This oscillating movement is commonly called " ring around absorbing flowing mode " and " can publishes referring to Grasselli and Bulkin Chemistry divides Analyse( Chemical Analysis) the 223rd to 252 page of the 14th volume in the book " The analysis Raman Spectrum" (" Analytical, Raman Spectrometry") 1991, Wiley, NewYork.》

The oscillating movement of molecule character and composition to molecule when measuring with the form of Raman spectrum is distinctive, the technology that the height that therefrom available abundant structures information makes Raman spectrum become the composition of explanation polyester in its forming process needs.How finishing with online daily method that this work was both unclear neither be obvious.Composition this purpose of continuous monitoring formation superpolymer realizes in the present invention in the polyester manufacture process.Like this, any polyester, its raw material can comprise that the composition and property of two acids and glycols, diester class and glycols, hydroxycarboxylic acid, hydroxycarboxylic acid esters class or their combination can be monitored in its building-up process according to the present invention.

In raman spectroscopy, observed signal is the convolution of desired signal and instrumental response value always.Generally, instrumental response value will make the signal of expectation broaden, move or twist.But method of the present invention makes energy measurement and offsets long-term and variation and the instability in each element of Raman spectroscopy instrument in a short time.This is by being described in U.S. Patent No. 5,455, and a reference technology in 673 realizes, it gathers the convolution spectrum of chemical sample and a kind of reference material in the reacting material flow simultaneously, and at this moment all spectrum all is placed in the identical instability environment.

Though the convolution process is non-linear in observed spectrum, can be expressed as product in time domain.The FT technology generally is used to finish to the conversion of time domain or from time domain and transforms.In time domain, going the convolution process is division intuitively, promptly uses the plural number (it real number and imaginary number component be made of) of instrument response function divided by observed signal.

Detecting device is monitored the spectrum of chemical composition of sampling and the spectrum of suitable reference material continuously.The convolution spectrum of reference material is also referred to as convolution reference spectrum here.Spectrum segment by all randomness instability with instrument radiation source and/or mechanical instability institute convolution known spectral characteristic.This convolution reference spectrum by instrument with the identical mode institute convolution of convolution spectrum of chemical composition of sampling, the latter is also referred to as convolution sample spectrum at this.

For putting into practice the present invention, suitable daily mathematical operation also is useful.The spectrum of collecting carries out mathematics manipulation with a kind of standardized method, and it has offset all other variations except that the detector noise variation of randomness.In this process, following spectral information is important: the reference spectrum of convolution sample spectrum, convolution reference spectrum, standard, the sample spectrum and the convolution function of standard.

Convolution sample spectrum S ' is the numeral of the Raman spectrum of unknown sample material (x), is obtained by the spectrograph detecting device.This spectrum is influenced by the instability of instrument (laser instrument and/or machinery) and the structural change in the sample simultaneously.

As mentioned above, convolution reference spectrum R ' (x) comprises the spectrum segment that has the known form characteristic, and it is with all instrument instability institute convolutions.This spectrum segment must be with the convolution function identical with convolution sample spectrum by convolution.

People can be offset convolution function c (x) because the changeability of radiation source and/or the variation that mechanical instability caused of instrument, and it is included as standard spectrum is converted to convolution spectrum or information necessary conversely.

Standard reference spectrum R (x) is a kind of selected spectrum, and it should be potential true representative in the reference spectral shape of convolution.This standard reference spectrum can be the theoretic mathematical notation of the constant part of convolution reference spectrum; It also can be the convolution spectrum of prior reference material of gathering, and the latter has been overregulated or smoothing.Preferably, it is by the convolution spectrum of the repeatedly reference material of gathering is in advance averaged the spectrum that obtains.Wish that a spectroscopic data of collecting is carried out " linearization " these available various interpolating methods with respect to horizontal ordinate to be finished, such as people such as those W.H.Press " The numerical value disposal route: The technology that science is calculated" (Numerical Recipes:The Art of Scientific Computing,) 1986, the Cambridge University printshop, the 77-89 page or leaf is described.Is useful especially in the described cubic spline function interpolation method of 86-89 page or leaf to reaching this purpose.The spectrum that is used to provide standard reference spectrum needn't obtain from the identical instrument of convolution spectrum that is used to gather sample and reference material.

Preferably, obtain spectrum R ' (x) and S ' (x) after, with the FT method they are transformed in the time domain, as, for example, The numerical value disposal route: The technology that science is calculated381-383 page or leaf and 407-412 page or leaf are described like that.When R (x) also can be transformed into time domain, become R ' FT (x) by the FT that removes R (x) and measure c (x).Because the matrix of expression R (x) and R ' FT (x) comprises plural number, this division must suitably be considered real number and imaginary number component simultaneously.

The convolution function c (x) that calculates is comprising variation and the instable essential information of distinguishing the instrument that exists in the spectrum data gathering process.Use then c (x) divided by (x) FT of S ' (the two is the matrix that contains plural number) to obtain the FT of S (x).By calculating inverted-F T based on this result, promptly obtain standard sample spectrum S (x), it has accurately represented the composition of sample.

If desired, S (x) is available, for example, makes the program of curve smoothing handle or go to obtain the difference quotient of spectrum.These programs may be useful when spectrum is used to duplicate when extracting quantitative composition information.The curve smoothing method is described in A.Savitsky and M.J.E.Golay, Anal. Chem.,1964, the 36 volume 1627-1639 pages or leaves.

The standard sample spectrum S (x) of Huo Deing is the spectrum that produces from the chemical composition of sampling after all the randomness instrumental variabless except that the detector noise of removing randomness in the methods of the invention.Thereby this spectrum will only change with chemical composition and make the accurate quantitative test of sample become possibility.

The typical Raman spectrum system that is illustrated among Fig. 2 comprises radiation source 1, optical waveguides 2, beam splitter 10, ray is sent to the parts of sample position at a distance, comprise and excite conduit 2A, 2B, 2C and 2D, radiant rays wave filter 3A and 3B, optical detector 4 and 13, radiant rays wave filter 5A and 5B, collecting duct 6A and 6B, spectrograph connector 7 and spectrograph 8, it comprises optical dispersion element, array detector 16 and has the computing machine 19 of suitable daily mathematical operation software.The convolution spectrum of gathering sample 17 and reference material when this system uses becomes possibility.This system is that the various assembly of following narration constitutes.

In embodiment preferred, radiant rays is sent to sample and reference material and comprises fiber optic cable from conduit 2A, 2B, 2C, 2D, 6A, 6B, 6C and 6D that this spreads out of.Expectation has many other light transmission waveguides also can satisfy this purpose, comprises the combination of optics such as level crossing, lens or hollow light pipe.But the fiber optic cable that comprises the quartzy core body of melting, the quartzy covering of coating melting and polyamide buffering is preferred, because they can provide the method for easy and the most effective transmission radiant rays in preferred diode laser wavelength coverage.

Discussed as the front, long distance uses optical fiber to have the technical difficulty that accompanies with it.Many methods that the front was described are enough to allow to use long optical fiber to position at a distance.A kind of is a kind of simple structure and the method that can insert easily and replace in instrument through preferable methods.

In embodiment preferred, conduit also further comprises optical filter 3A, 3B, 5A and 5B, and wherein each is between two little collimation lenses.These optical filtering apparatus have maximum output through optimization, are connected to and excite and collect on the relevant fiber optic cable.This optical filtering apparatus is preferred, because they are little, compact, solid, and shift out easily and replaces.Expection has other filtering method and is described in the document and/or can have bought from market, the purpose of removing the scattered ray of not wanting that also can be used for reaching.According to the present invention, incident radiation is general earlier by bandpass filter 3A and 3B before entering sample and reference material, and is collecting later on by rejection filter 5A and 5B.

Provide the optic probe 4 and 13 with the linkage interface of the sample material 17 of process stream and reference material must have suitable characteristic to satisfy the needs of the inventive method operation.At the technology interface, this probe should send incident radiation to sample, also will collect the scattered ray that sends from sample.Key is that this linkage interface should be stable under the operating conditions of processing line; Connect boundary's little variation in place and may cause output efficiency aspect tremendous loss.The chemical technology condition usually is harsh; For example, the processing line of production of polyester is the temperature between 150 to 300 ℃ and high to 20 usually, and 685kPa (3, the operation down of pressure condition 00psi).Exacting terms has limited the material type that is used for setting up linkage interface like this.

Of the present invention in embodiment preferred, used a kind of fibre-optical probe, it is by constituting in the metal shell that the quartz fiberoptic cable with metal coating, melting is welded to protection; This probe is described in the common unsettled u.s. patent application serial number No.08/450 that people such as Buchanan issue on May nineteen ninety-five 25, and in 597, title is " a solid spectrum optic probe ".This probe is directly inserted in the production line, and aforementioned optical filtering apparatus is connected opposite one end of probe terminal.This probe designs provides a kind of simple and reliable method, is used in the harsh physical environment of manufacturing process to the Chemical composition that optical sampling.The benefit that adds of this design is, if when damage takes place, probe takes out easily and replaces, and need not to carry out optical correction in daily use.

The optical dispersion element is the scattered ray that is used for separating various energy levels.Generally, spectrograph 8 must have suitable resolving power to separate radiation level to required program.It also should be efficient, so that radiation loss reduces to minimum.

Useful commercially available spectrograph constitutes as dispersion element with standardized grating.According to the space between institute's groove bar on the size of spectrograph carton and crate and the grating, this instrument can have different resolution characteristiies.Other commercially available spectrograph is with specially designed haloing dispersion element, and it has the output characteristics of enhancement.Of the present inventionly use the single grating spectrograph have fixed grating through embodiment preferred, it comes chromatic dispersion light like this, and the wavelength of 800 nanometer to 1000 nanometer range is incident upon in the surveyed area.Such high-quality instrument can have been bought from various sale mechanism.

For instrument is turned round effectively, array detector 16 is very important.In order to obtain useful spectrum under the condition that has bubble or particle to exist at process stream, detecting device must have the passage of many tight arrangements so that collect data simultaneously.Two kinds of existing detection systems that are generally used for this purpose are charge-coupled device (CCD) and photodiode array (PDA).CCD is preferred, because these detecting devices have extremely low levels of background noise, is very sensitive, and can makes two-dimensional array, thereby allow to form the image of many spectrum on single detecting device.This multiplex ability can help to reduce the expense of instrument and the means of using the two-beam standardized method are provided, as in U.S. Patent No. 5,455, described in 673 like that.This standardized method has improved precision and has helped to reduce the expense of sampling.

The CCD detection arrays of different shape and size all can have been bought from market.The generic array size is 512 * 512 pixels and 386 * 576 pixels.Array also can buy of other big specification such as 256 * 1024 or 1024 * 1024 pixels.This class detecting device must be cooled to below the room temperature, so that the levels of background noise of interference reduces to minimum.This can reach by cooling off with liquid nitrogen, water or air.Some CCD device uses a kind of technology that is called as multi beam phase modulation (MPP), and it reduces background signal and noise level, thereby can reach required performance under the condition that cools with air.

, wish noise is reduced to minimum of the present invention in embodiment preferred, signal increases to maximum, must keep instrument amount reduce to minimum.For this purpose, wish with suitable air cooled MPP, CCD detecting device.512 * 512 pel arrays are preferred because it can provide suitable spectrally resolved/cover and allow to carry out and multichannelly detect simultaneously.

The spectrograph of spectrometer system, detecting device and laser part generally are not designed to tolerate the environmental impact of Production Regional.Therefore preferably these devices are installed in the safe controlled environment, away from the sampled point of production technology; Optical fiber extends between controlled environment and the technology sampled point, and is connected to optical detector, and the latter is inserted in the production line.

The spectrum of collecting in described Raman spectrum system is the indication of the chemical composition of the material that flows in production technology.The precision of this method and accuracy can be strengthened by the preferred version that uses the assembling instrument, though the combination of other parts also is useful.

The final analysis result is produced interference in some meetings or coarse phenomenon need be understood and control, to obtain high as far as possible accuracy and precision.These phenomenons have: " cosmic rays " incident; Bubble in the technology, particle and turbidness; The check point sampling; The laboratory sampling error; And the vibration of instrument component, motion and move.

" cosmic rays " incident often is called as peak value, is to appear on the CCD detecting device in the randomness mode.They are considered to caused by the high energy particle from the outer space, cause spectrum peak big, contaminative when the collision of they and CCD detector element.Generally, the peak value that is produced by these incidents is very narrow, and it is wide typically to be 1 to 5 pixel.Cosmic ray event be rare, uncertain, though the frequency that has some evidences to show this class incident is active relevant with the intraday time with sun credit class.

The cosmic rays peak value is a trouble, because they add a big signal in spectrum, it doesn't matter with producing material for it.Fortunately, have the daily operational method of some simple mathematical to can be used to proofread and correct or these spectroscopic datas of cancellation in peak value.The daily operational method of a kind of this class is described in people such as Takeuchi, Appl.Spec.,1993, the 47 volume 129-131 pages or leaves.

Bubble, particle and turbidness can influence observed spectrum by the part of area of the sample is darkened, thereby spectral intensity is changed, and spectral intensity is relevant with changeability in the volume of sample.By using the multi-channel detection system, all energy levels of scattered ray can both side by side be observed.Bubble, particle and turbidness act on spectral response in a kind of mode that is similar to the unordered tree multiplication, and it allows to use a kind of correction and makes spectrum normalization.This normalization program generally is used for standard sample spectrum, has proofreaied and correct the deviation in the material volume of being sampled by incident radiation.

The simplest normalization scheme is to utilize a kind of internal standard, and it is the indication to the amount of sample material.For PET type polyester material, a kind of making is positioned at about 1610cm ^-1The scheme of the peak area normalization of the ring around absorbing flowing mode at place is convenient and useful.This mode of vibration is directly relevant with the number of the terephthalate ring of sampling, thereby makes it can be used to the changeability of check sample volume.This scheme, though because its simplicity is preferred, be not the unique method that can reach normalization, other can make the mathematical method of spectrum normalization also can be used.

Observed Raman spectrum relates to be sampled the combination of the shuttle belt of forming in the material.Yet the scattering efficiency that every kind of specific oscillating movement has is relevant with the polarizability of this oscillating movement.Because this point.The simple analysis of shuttle belt can not directly provide required composition information.Because what do not obtain that sample forms directly measures, so must set up the bearing calibration that spectral characteristic that handle observes and required analytical information pass are linked up.For setting up bearing calibration, being taken out and carry out analysis to measure from chemical technology with the sample of specific collection spectral correlation in time provides chemical composition information.Because the spectrum of gathering is by the instability of instrument institute convolution, they preferably were converted into standard spectrum earlier in the past setting up bearing calibration.This can use and be disclosed in U.S. Patent No. 5,455, and the convolution function in 673 is realized by measuring.The preferred adamas of using for this method of reference material.

At the Raman spectrum of the Chemical composition that of more many known its compositions of many wavelength location, preferably its standard spectrum makes the multivariate calibration method of setting up a kind of composition-intensity relevant (CIC) become possibility.Be elected to be the spectral characteristic that the wavelength of setting up CIC depends on specific component, its concentration in Chemical composition that is to want to be determined.For each component,, then to prepare other CIC bearing calibration of branch if its on-the-spot concentration in composition is to want in any given time monitoredly.

Use and set up bearing calibration, comprise multivariate calibration and partially least square solution return, be described in people such as Martens show " Multivariate calibration" ( Multivariate Calibration) in a book 1-6,11-22,25-30,73-78 and the 116-125 page or leaf, New York published this book by Wiley in 1989.The concentration of other Raman spectrum peak area and the chemical substance method that connects of class mutually is described in U.S. Patent No. 4,620, in 284.

For the ethylene glycol that from the potpourri of dimethyl terephthalate (DMT) (DMT) and ethylene glycol (EG), wherein also can further comprise limited concentration is modified body such as cyclohexanedimethanol (CHDM), the polymkeric substance for preparing the PET type, the importantly degree that will carry out in each time supervision ester exchange reaction of technological process.This can realize by measure to form methyl esters end group (from DMT), hydroxyethyl end group (from EG) in the polymer composition and be contained in the concentration that inner ethylidene in two (2-hydroxyethyl) esters (BHET) of intermediate terephthalate is connected part.In these species of on-site measurement each needs each other concentration-intensity relevant nature (CICs).The amount of measuring the ethylene glycol modification body that exists at any given time needs additional C IC.

The vibration of various instrument components, motion and move and in observed spectrum, to cause unforeseeable variation.The error pattern that induces be difficult to expect and may cause inaccurate result, it will cause limited accuracy, therefore the influence of importantly eliminating vibration in the instrument, motion and moving maybe reduces to influence minimum, and this can make it " curing " by the parts that firmly install instruments and accomplish in solid structure.A kind of instrument solidifies better, and the precision that it finally can reach is also higher.

Sample probe can be placed in any position in the chemical fabrication processes flow process, is desirable but generally the place that can provide the CONTROL PROCESS Useful Information and can be provided as the analytical information that the purpose of correction uses is provided probe.

A place of preferably laying the sample probe in polyester production process is near local completely near first step reaction in the technology.This provides a kind of method, can determine rapidly about the degree, the glycols that react molar ratio, glycol or the diacid of acids and/or diester class to be modified the percentage of body and the analytical information of extent of polymerization by it.This category information can be used to improve to the control of the first step of technology and improves control to downstream process.

Following embodiment further illustrates the present invention.

Embodiment 1-confirms the ability of this method in batch process

The technical capability of this monitoring method is confirmed under the condition that is similar to those production technology environment in the laboratory reaction container.The ester exchange reaction of terephthalic acids dimethyl ester (DMT) and ethylene glycol (EG) can be used the on-the-spot continuous monitoring of Raman spectrum when sample takes out periodically from reaction vessel.Then carry out second time reaction, be used for data that the comparison Raman spectrum records and the data that record with NMR (nuclear magnetic resonance), thus the validity of confirmation bearing calibration.

Raman instrument comprises krypton ion gas laser (available from the Lexel company of CA Fremont), operates in 752 nanometers, as radiation source.The plasma lines that obtains by the laser production process ray focusing during in 200 microns core bodys by the dielectric bandpass filter the filtering of incident radiation bundle, core body is given the sample probe that directly inserts in the reaction medium ray transmission for poly-imines silica fibre optical cable buffering, melting, this fiber optic cable.

Scattered ray is received by six 200 micrometer fibers optical cables near excitation fiber.Collect optical fiber Instrument SA 320 type spectrographs (the Edison company product of NJ) dorsad for these six.These optical fiber are aligned to linear array and are located immediately at the place ahead of beam inlet slit.

The inlet lens at first are to be used for making light parallel, then its rejection filter by Kaiser lens (the Ann Arbor company of MI) haloing form, it can eliminate all elastic scattering rays basically, and finally through the ray focusing of filtering on the entrance slit of spectrograph.Dispersed light detects and is converted into electric signal with the CCD detecting device of ISA cooled with liquid nitrogen.

This instrument is to control with the software that can collect the sequence data file continuously.Order spectrum was compared after gathering to remove the peak value that cosmic rays causes in a pair of 30 seconds.Remove behind the peak value average two width of cloth spectrum.Be positioned at 1610cm ^-1The aromatic ring breathing vibration spectral signature at place is used as and is disclosed in U.S. Patent No. 5,455, and the convolution reference spectrum of the standardized method in 673 is to remove the variation of bands of a spectrum shape and position.Be positioned at 1610cm ^-1The integral area of the aromatic ring breathing vibration mode at place is used to normalization.

Resulting standardization waveform comes smoothing by 3 half width Gauss broadening functions and half past one width Lao Lunci stricturization function in Fu Li leaf territory.Calculate the secondary difference quotient of data and resulting data through standardization and smoothing are used for setting up CIC and proofread and correct, can use partial least square method (PLS) data analysis software bag (as the A/S type software package UNSCRAMBLER that supports from the computing machine of Norway Trondheim).

About 1065 gram DMT and 865 gram EG are added in the big reaction vessel.Container be connected with one be equipped with optic probe, thermopair, stirrer, condenser and sample tap through specially designed lid.Clean and nitrogen stream that relax is passed into the reaction mixture top and does not contact oxygen with the protection potpourri.

Reaction mixture is heated to 180 ℃ carefully when gathering Raman spectrum data.After collecting some baseline spectrum, in potpourri, add about 0.20 gram manganese acetate catalyst.After a few hours, temperature of reaction rises to 195 ℃, after some times, rises to 210 ℃.

During reaction is carried out, take out a sample and analyze to measure the number of fragrant terephthalate ring with the NMR instrument, be referred to as-T-; The methyl esters end is referred to as-CH ₃The hydroxyethyl end is referred to as-OH; Inner ethylidene connects partly, is referred to as-2-; And free ethylene glycol EG.

Figure 3 shows that methyl esters terminal number purpose proofreaies and correct with the reacting value that confirms.Methyl esters end group-the CH that records ₃Number be normalized to terephthalate ring-T-, thereby provide the direct measurement of ester exchange reaction degree.The related coefficient that this calibration curve presents is 0.9999, the triumph of all being good in showing Raman optical spectrum method required analysis result being measured in the whole compositing range of ester exchange reaction.

Fig. 4 shows the figure of the various parameters that record in the entire reaction.Indivedual spectrum need be measured once by about per minute, and initial 20 minutes data are when 180 ℃ of vessel temps and do not add under the condition of catalyzer and obtain.After adding catalyzer, reaction rate promptly increases sharply.After three hours (spectrum several 180), temperature of reaction rises to 195 ℃, and (spectrum several 230) temperature further rises to 210 ℃ after four hours.

Remarkable ability when the data acknowledgement among Fig. 4 comes some important components in the assaying reaction with the present invention.The methyl esters terminal number is to form the indication of intermediate B HET degree and is a kind of important criterion for good polymkeric substance manufacturing.Inner ethylidene unit is directly relevant for the degree of polymerization and molecular weight, and it is other critical nature.

Embodiment 2- Analysis in the production of polyester reaction process

For confirming the present invention as a kind of scene, online, the applicability of quantitative analysis tools under production environment, Raman instrument is installed in the place near the production of polyester line.A kind of structure as above-mentioned common u.s. patent application serial number No.08/450 unsettled, issue on May 25 nineteen ninety-five, 597 title is that disclosed solid detector is made in the terminal polyester materials flow of charging into mobile, melting of sampling by this sampling device in " solid spectroscopic optics detector ".This specific production line is to be designed to make by DMT, EG and CHDM to produce the PET that ethylene glycol is modified.Measuring method is proved in six time-of-weeks.All obtained corresponding to the analysis data of first step reaction (transesterification) degree, the percentage composition that glycols is modified body to the molar ratio and the CHDM ethylene glycol of acids etc.

The formation of Raman instrument comprises 2.0 watts of many types of formula diode lasers that excite operation with 800 nanometers; It is coiled in (the Spectra Diode Lab.Inc product of San Jose, CA type numbering SDL-2372-93) on 100 microns the quartz silica core body fiber optic cable.The incident ray fiber optic splitter (O of Ontario, Canada ₂Optics LtD. product, model FOBS-12-555-MMM-750-50/50) is divided into two bundles.Two beam lines are focused on the quartz silica fiber optic cable of other 200 microns core bodys of branch, polyimide buffering (the Fiberguide Industries product of NJ.Stirling).These two strands of optical fiber are sent to ray on sample probe and the reference probe.The sample probe is directly inserted in about 40 meters technological process.

Ray before entering probe out of the ordinary in the per share fiber optic cable is filtered.The wave filter of design can only transmit narrow energy band (the Omega Optica company product of Brattleboro, VT model 800 BP10), and be inserted into (Oz OpticsLtD. product, model ND-200-55-750-M-30) on the fixing fiber optics wave filter holder device.The reference probe is used to illuminate little adamas fragment, and the latter is used as reference material.The sample probe is by in the materials flow of flange openings insertion process.

Scattered radiation from reference and sample is divided other, is positioned near 200 micron optical fibers at excitation fiber place and collects.The scattered radiation of collecting is filtered to remove nearly all Rayleigh scattering line before returning optical fiber entering.This wave filter (Omega Optical company product, model 800REFLP) is placed in (Oz Optics LtD. company, model ND-200-55-750-M-30) on the fixing optical fiber filter holder device and be designed to the undesired radiation of filtering effectively and allow to collect the Raman scattering line of being wanted simultaneously.

Two strands are returned optical fiber and are drawn towards the back of the body towards ISA 320 spectrographs.Optical fiber is aligned to linear array and is located immediately at the place ahead of entrance slit.Dispersed light detects and is converted into electric signal with the CCD detecting device of ISA cooled with liquid nitrogen.

This instrument is controlled with the software that can collect the sequence data file continuously.Gather each to 30 seconds sequence spectrum and compare to remove the peak value that cosmic ray cause, it is average again two bundles to have been removed the spectrum of cosmic ray peak values.With being described in The numerical value disposal route: The technology that science is calculatedOne book ( Numerical Recipes: The Art of Scientific Computing) the cubic spline function interpolating method of 86-89 page or leaf provides through the reference of convolution and the equidistant horizontal ordinate data in the sample spectrum.Standardization and normalization can be carried out as described in the example 1.The standardization waveform that obtains in Fu Li leaf territory with 9 half-breadth Gausses function and 7 half-breadth Lao Lunci function smoothing that narrows down that broadens.Five orders through the standardization waveform of smoothing together by average so that per five a minutes data point to be provided.

Sample probe present position in process stream is near the place of finishing in the ester exchange reaction supposition.The process environments internal temperature is about 235 ℃, about 206.85 kPas of (gauge pressure) (the closing 30psig) of pressure.Thief hatch nestles up the sample probe, takes out hour oligomer sample once every 12 hours.This sample is analyzed to measure the degree of ester exchange reaction through NMR.

Being used to constitute CIC through secondary difference quotient and standardized level and smooth spectrum and proofreading and correct corresponding to the analysis component of concentration known in time.Correction is to form with partial least square method (PLS) data analysis software bag (the A/S type software UNSCRAMBLER that the computing machine of Norway Trondheim is supported).

Fig. 5 is presented in nearly six time-of-weeks to measuring the data (representing with solid line) that the ester exchange reaction degree is measured gained result (point with the empty circles mark is represented) and obtained with the Raman instrument through NMR from the sample that extracts.The NMR data are showed the process of wide variation, and its mid point is a dominant trend in the data to the deviation of another point.The main source that changes can suppose by sample take out, inherent process changes and analysis to measure etc. causes.

The uncontinuity of Raman spectrum data is by not refilling liquid nitrogen container or loss of data once in a while is caused.

The statistical study of process data confirms this observation, i.e. Raman spectrum data point to the change of another point is measured much smaller than NMR.The Raman method confirms to have good relative precision, about 0.1%.The largest source that changes in the NMR data is considered the mode that sample takes out from flow process in the method for sampling, this does not make us being surprised.

Except that higher precision, the Raman method is very clear to provide more frequent sampling, has reduced needs that sample shifts out and analyzed than NMR to have the faster turnaround time.More frequent sampling provides character that vacuum changes in the better understanding course of reaction and the method that continues.Reduce the needs that take out sample and significantly reduced injured risk.Turnaround time provides the method that obtains more positive technology controlling and process strategy faster.Use the present invention clearly to make more frequent and more accurate variable measurement become possibility.

Example 3-confirms the ability that this method is analyzed the dimethylbenzene that mixes

The technical capability of measuring the composition of other Chemical composition that with this method is proved by the dimethylbenzene sample for preparing a cover mixing.This cover sample is by the varying number of every kind of component of weighing carefully and is mixed into potpourri and makes, and calculates volumetric molar concentration percentage and as actual value, represents with STD in the table 1 below.

The formation of Raman instrument comprises 2.0 watts of multimode diode lasers that excite operation with 800 nanometers; It is coiled on 100 microns the quartz silica core body fiber optic cable (the SpectraDiode Lab.Tnc product of San Jose, CA model SDL-2372-P3).Incident radiation is divided into two bundles with fiber optic splitter (the Oz Optics Ltd. product of Ontario, Canada Carp, model is FOBS-12-555-MMM-750-50/50).Two beam lines are focused on the quartz silica fiber optic cable of other 200 microns core bodys of branch, polyimide buffering (the Fiberguide Industries product of NJ.stirling).These two strands of optical fiber are sent to ray on sample probe and the reference probe.

Radiant rays before entering wiping head out of the ordinary in the per share fiber optic cable is filtered.The wave filter of design can only transmit narrow light (the Omega Optical company product of Brattleboro that can be with, VT model 800 BP10), and be inserted into (OzOptics Ltd. product, model ND-200-55-750-M-30) on the fixing fiber optics wave filter holder device.

Reference and sample fibre-optical probe all are built into indoor heating system.The reference probe is used to illuminate little adamas fragment, and the latter is used as reference material.The sample probe then is inserted into 316 stainless steel sample hoses, wherein is placed with the dimethylbenzene sample of mixing.

Scattered radiation from reference and sample is divided other, is positioned near 200 micron optical fibers at excitation fiber place and collects.The scattered radiation of collecting is filtered to remove nearly all Rayleigh scattering line before returning optical fiber entering.This wave filter (Omega Optica company product, model 800REFLP) is placed in (Oz Optics LtD. company on the fixing optical fiber wave-wave device holder device, model ND-200-55-750-M-30) and be designed to the undesired ray of filtering effectively, allow to collect the Raman scattering line of being wanted simultaneously.

Two strands are returned optical fiber and are drawn towards the back of the body towards an Acton SpectroPro type spectrograph (the Acton Research Corporation product of MA.Acton).Monochromator is to form with the rotary type optical-mechanical system that has three scattered gratings.These gratings are: 150 grooves/mm, glitter in 750 nanometers; 300 grooves/mm, glitter in 750 nanometers ' 600 grooves/mm, glitter in 750 nanometers.300 grooves/mm grating is used as analyzes and provides about 1700cm ^-1Spectrum cover.

The fiber adapter that has 8 200 microns input ends is connected the porch of monochromator so that can collect eight Raman passages.Optical fiber is lined up linear array and is located immediately at the front of entrance slit.One in these eight monochromator optical fiber is connected to sample probe optical fiber, and another is connected to reference probe optical fiber.(Trenton, the CCD detecting device of a kind of thermoelectric-cooled NJ) detects and is converted to electric signal to dispersed light by Princeton Instruments company.The CCD detection lug is the detection system that has 512 * 512 pixels, illuminates from behind that Techtronix company produces.

This instrument is to be controlled by the CSMA data acquisition software that Princeton Instrument company provides; Gather 30 seconds spectrum.A kind ofly be used to reference and the sample spectroscopic data of linearization with respect to the convolution of horizontal ordinate as employed cubic spline function interpolating method in the example 2.Be described in U.S. Patent No. 5,455, the standardized method in 673 is used for eliminating the change of bands of a spectrum shape and position.What obtain comes smoothing in Fu Li leaf territory with broaden function and the narrow function of the wide labor Lenze's stenosis of half past two of 3 half-breadth Gausses through standardized waveform.

The standard sample spectrum that obtains from Sample A-K is used to combine with partial least square method (PLS) data analysis software bag (the A/S type software UNSCRAMBLER that the computing machine of Norway Trondheim is supported), to produce the compensation line of every kind of component in the xylene mixture.This compensation line is used to provide the composition information from each sample.

Sample L-Q forms one and overlaps the practical independent samples of providing evidence.Also by measuring with the similar mode of Sample A-K, it provides the standard spectrum of per sample (p.s.) to these samples.Correction function is used for the measurement result that each standard spectrum promptly provides respective samples composition aspect.

The monochromator wavelengths centered is deliberately moved to 899 nanometers causing the instability of instrument from 901 nanometers, and measure sample G and L-Q (being labeled as sample R-X again) once more thus provide a cover new standard spectrum.Each standard spectrum is used the measurement result that correction function provides sample to form.

In the table 1 below, indicating a hurdle of the present invention is to form from the mole percentage of the xylene mixture of their raman spectroscopy with method of the present invention.These numerical value are shown in " difference " hurdle with the differing of actual percentage that is listed in " STD " hurdle.The component sign is as follows:

The P=P-xylene, M=m-xylene, O=o-xylene

Table 1 sample is formed STD difference A P 39.86 39.84-0.02 of the present invention

M 35.22 35.19 -0.03

O 24.91 24.97 0.06B P 39.98 40.10 0.12

M 25.01 25.07 0.06

O 35.01 34.83 -0.18C P 34.97 34.99 0.02

M 25.13 25.21 0.08

O 39.91 39.80 -0.11D P 34.78 34.81 0.03

M 39.93 39.94 0.01

O 25.29 25.25 -0.04E P 39.95 39.83 -0.12

M 25.08 24.92 -0.16

O 34.97 35.25 0.28F P 33.34 33.28 -0.06

M 33.32 33.44 0.12

O 33.33 33.28 -0.05G P 33.42 33.51 0.09

M 33.23 33.11 -0.12

O 33.35 33.37 0.02H P 25.12 25.14 0.02

M 39.94 39.91 -0.03

O 34.94 34.95 0.01

P 35.04 35.05 0.01

M 39.97 39.93 -0.04

O 24.99 25.02 0.03J P 39.97 39.93 -0.04

M 35.01 35.11 0.10

O 25.02 24.95 -0.07K P 24.97 24.92 -0.05

M 35.09 35.11 0.02

O 39.95 39.97 0.02L P 30.14 30.16 0.02

M 29.92 29.92 0.00

O 39.94 39.92 -0.02M P 30.03 30.07 0.04

M 39.90 39.82 -0.08

O 30.07 30.12 0.05N P 39.96 39.96 0.00

M 29.95 30.07 0.12

O 30.09 29.97 -0.12O P 35.01 34.85 -0.16

M 35.03 34.89 -0.14

O 29.97 30.26 0.29P P 35.00 35.12 0.12

M 30.01 29.90 -0.11

O 34.99 34.98 -0.01Q P 30.03 30.04 0.01

M 34.99 35.00 0.01

O 34.98 34.97 -0.01R P 33.42 33.40 -0.02

M 33.23 33.15 -0.08

O 33.35 33.45 0.10S P 30.14 30.12 -0.02

M 29.92 29.76 -0.16

O 39.94 40.12 0.18T P 30.03 29.91 -0.12

M 39.90 40.08 0.18

O 30.07 30.01 -0.06U P 39.96 39.79 -0.17

M 29.95 29.88 -0.07

O 30.09 30.33 0.24V P 35.01 34.92 -0.09

M 35.03 35.03 0.00

O 29.97 30.05 0.08W P 35.00 35.05 0.05

M 30.01 30.15 0.14

O 34.99 34.80 -0.19X P 30.03 29.86 -0.17

M 34.99 35.07 0.08

O 34.98 35.07 0.09

Demonstrate in the table 2 below to the standard error after the potpourri A-K correction and according to the present invention, the standard error of the two cover sample L-Q that measure by the Raman spectrum of sample that the convolution function is applied to record and the value of prejudging of R-X potpourri also comprises corrected value when not using the inventive method and the error numerical value of the value of prejudging for comparison purpose in table 2.

Table 2

Relatively The present invention Standard error P M O P M OSample A-K 0.22 50.191 0.338 0.066 0.084 0.110 sample L-Q 0.33 60.329 0.591 0.082 0.096 0.134 sample R-X 3.595 3.949 7.495 0.109 0.116 0.148

Find out that the present invention also makes the numerical value of standard error obviously reduce for check sample series A-K even can know by the clauses and subclauses of table 2.For sample series L-Q as confirmation, improvement even bigger.Yet only under the situation of this cover sample of R-X, at this moment the monochromator wavelengths centered is deliberately moved 2 nanometers to cause the instability of spectrophotometer system, and the present invention has confirmed its most wonderful advantage, and it significantly reduces the standard error of the value of prejudging.

The present invention is especially with reference to embodiment preferred and detailed description.Still can implement within the spirit and scope of the present invention to change and modify but should understand.

Claims (22)

1. method with one or more selected components in the Raman spectrum Quantitative Monitoring Chemical composition that, it comprises: with a kind of be that monochromatic radiation source shines a kind of reference material simultaneously and contains the Chemical composition that of one or more chemical compositions substantially, described radiation is sent to described Chemical composition that by described radiation source and connects on the optic probe on boundary, and described radiation source is connected on the described probe by a kind of conduit that excites; Gathering the convolution Raman spectrum of described reference material and the convolution Raman spectrum of described Chemical composition that simultaneously more than a kind of wavelength place by a spectrograph, described spectrograph is connected on the described optic probe by collecting duct; Select the standard Raman spectrum of described reference material; Convolution Raman spectrum and standard raman spectroscopy convolution function by described reference material; And use the convolution Raman spectrum that described convolution function is regulated described Chemical composition that, thereby produce the standard Raman spectrum of described Chemical composition that, improvement wherein comprises:

Described optic probe is directly inserted in the Chemical composition that of chemical technology, the optic probe in this Chemical composition that is placed in away from described spectrograph; And the bearing calibration that will measure in advance is applied to the described standard Raman spectrum of the Chemical composition that of described chemical technology, thereby can be at the chemical technology scene, gathering the content of determining one or more selected components in the described Chemical composition that substantially simultaneously of described convolution Raman spectrum.

2. the process of claim 1 wherein that described radiation source is a kind of lasing light emitter.

3. the method for claim 2, wherein said lasing light emitter is a diode laser.

4. the method for claim 3, wherein said diode laser is a kind of multi-mode diode laser.

5. the process of claim 1 wherein that described conduit and the described collecting duct of exciting comprises a kind of optical waveguides respectively.

6. the method for claim 5, wherein said conduit and the described collecting duct of exciting further contains a kind of ray filter respectively.

7. the process of claim 1 wherein that described optic probe comprises at least two kinds of light transmitting fibers.

8. the process of claim 1 wherein that described spectrograph is a kind of color dispersion-type spectrograph or a kind of Fourier Tranform type interferometer.

9. the process of claim 1 wherein that described bearing calibration comprises concentration-intensity (CIC) multivariate calibration of being correlated with, described concentration-intensity correlation-corrected is that the Raman spectrum by the potpourri of the chemical composition with concentration known records.

10. the method for claim 9, the described Raman spectrum of wherein said potpourri comprises the Raman spectrum of standard.

11. the process of claim 1 wherein that described reference material comprises adamas.

12. the process of claim 1 wherein that described Chemical composition that comprises by reacting the composition of the formation polymkeric substance that low-molecular-weight compound of reaction produces.

13. the method for claim 12, wherein said low-molecular-weight compound of reaction comprises diol compound and dicarboxylic acid compound or dicarboxylate compounds.

14. the method for claim 13, wherein said diol compound comprises ethylene glycol, 1,4-cyclohexanedimethanol, 1,4-butylene glycol, diglycol, triethylene glycol, polyglycol, polypropylene glycol, two (2-hydroxyethyl) esters of terephthalic acid (TPA), two (the 4-methylol cyclohexyl methyl) esters of terephthalic acid (TPA) or terephthalic acid (TPA) (2-hydroxyethyl)-(4-hydroxyethyl cyclohexyl methyl) ester.

15. the method for claim 13, wherein said dicarboxylic acid compound comprise terephthalic acid (TPA), m-phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexane dicarboxylic acid or hexane diacid.

16. the method for claim 13, wherein said dicarboxylate compounds comprises dimethyl terephthalate (DMT), dimethyl isophthalate, 2,6-naphthalene diformic acid dimethyl ester, 2,6-naphthalene diformic acid dimethyl ester, 1,4-cyclohexane dicarboxylic acid dimethyl ester, dimethyl adipate, two (2-hydroxyethyl) esters of terephthalic acid (TPA), two (4-methylol-cyclohexyl methyl) esters of terephthalic acid (TPA) or terephthalic acid (TPA) (2-hydroxyethyl)-(4-methylol cyclohexyl methyl) ester.

17. the method for claim 13, wherein said low-molecular-weight compound of reaction comprises ethylene glycol and terephthalic acid (TPA).

18. the method for claim 17, wherein said compound of reaction further comprises cyclohexanedimethanol.

19. the method for claim 13, wherein said low-molecular-weight compound of reaction comprises ethylene glycol and dimethyl terephthalate (DMT).

20. the method for claim 19, wherein said compound of reaction further comprises cyclohexanedimethanol.

21. the method for claim 12, wherein said Chemical composition that further comprise poly-(ethylene terephthalate).

22. the process of claim 1 wherein that described Chemical composition that is included in the volatile material of distillation cat head.

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