Analysis method for sample components containing one or more of 1, 4-cyclohexanedimethanol, 1, 4-dimethyl cyclohexanedicarboxylate and dimethyl terephthalate

Abstract

The invention relates to the technical field of chemical detection, in particular to a method for analyzing sample components containing one or more of 1, 4-cyclohexanedimethanol, dimethyl 1, 4-cyclohexanedicarboxylate and dimethyl terephthalate. The analysis method comprises the following steps: sample pretreatment: pretreating a sample to obtain a liquid without mechanical impurities as a sample to be detected; determining and analyzing a to-be-detected sample: injecting the to-be-detected sample into a gas chromatograph for detection, and determining the nature by using an external standard method; the detection conditions are as follows: the detector is FID, and the temperature of the FID is 295-320 DEG C. The analysis method disclosed by the invention is simple, good in reproducibility, high in sensitivity, good in stability, simple to operate and high in analysis speed, can meet the analysis requirements of 1, 4-cyclohexanedimethanol, raw materials thereof and raw material hydrogenation products or samples containing or partially containing similar components, and omits the tedious operation of selecting and adding internal standard substances.

Description

Technical Field

[0001] This invention relates to the field of chemical testing technology, specifically to an analytical method for one or more sample components containing 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate. Background Technology

[0002] PETG is a transparent, amorphous copolyester, produced by the transesterification polymerization of three monomers: terephthalic acid (PTA), ethylene glycol (EG), and 1,4-cyclohexanediethanol (CHDM). Unlike PET and PCT, PETG exhibits outstanding toughness and high impact strength, 3 to 10 times that of modified polyacrylates. It also boasts a wide processing range, high mechanical strength, and excellent flexibility. Compared to PVC, it offers higher transparency, better gloss, easier printing, and environmental advantages.

[0003] Currently, the main method for preparing PETG's important monomer, 1,4-cyclohexanediethanol (CHDM), is a two-step hydrogenation route using dimethyl terephthalate (DMT). In the first step, the benzene ring of DMT is hydrogenated to form dimethyl 1,4-cyclohexanediethanolate (DMCD), and in the second step, DMCD is hydrogenated to generate CHDM.

[0004] Dimethyl terephthalate (DMT) is an important raw material for the preparation of 1,4-cyclohexanedimethyl methanol, and dimethyl 1,4-cyclohexanedimethyl acetate (DMCD) is an important intermediate product in the preparation of 1,4-cyclohexanedimethyl methanol. The hydrogenation products of dimethyl terephthalate contain, in addition to the target product 1,4-cyclohexanedimethyl acetate, various impurity components and possibly unconverted dimethyl terephthalate. The hydrogenation products of 1,4-cyclohexanedimethyl acetate contain, in addition to the target product 1,4-cyclohexanedimethyl methanol, methanol, various impurity components, and possibly unconverted dimethyl 1,4-cyclohexanedimethyl acetate. In China, the analysis of 1,4-cyclohexanedimethyl methanol and samples containing or partially containing similar components, such as raw materials and their hydrogenation products, is usually performed using gas chromatography or liquid chromatography.

[0005] CN111272900A discloses a gas chromatographic analysis method for 3-chloro-2,2-dimethyl-1-propanol, including sample preparation, gas chromatographic analysis conditions, and qualitative and quantitative methods. The chromatographic analysis conditions are: injection volume 1 μL; gas chromatographic conditions: retention at 60℃ for 4 minutes, then increasing to 250℃ at 20℃ / min and retaining for 10 minutes; using a TG-wax column (30m × 0.25mm × 0.25μm) and a flame ionization detector; the residence time of 3-chloro-2,2-dimethyl-1-propanol is 8.980 min; the quantitative method used is the internal standard method, with 1,3,5-trimethylbenzene as the internal standard, and a residence time of 6.650 min for the internal standard.

[0006] CN111855864A discloses a gas chromatographic analysis method for dimethylcyclopropane (2,2-dimethyl-1,3-epoxypropane) and neopentyl glycol (2,2-dimethyl-1,3-propanediol), including sample preparation, gas chromatographic analysis conditions, and qualitative and quantitative methods. The chromatographic analysis conditions are: injection volume 1 μL; gas chromatographic conditions: 60℃ for 4 minutes, then increased to 250℃ at 15℃ / min and held for 10 minutes; using a TG-1701ms column (30m × 0.25mm × 0.25μm) and a flame ionization detector; residence time for dimethylcyclopropane is 2.278 min, and for neopentyl glycol is 8.983 min; the quantitative method used is the internal standard method, with ethylene glycol as the internal standard and a residence time of 6.650 min.

[0007] CN113252831A discloses an ultra-high performance liquid chromatography (UHPLC) method for the analysis of methyl N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]carbamate, comprising: (1) preparing a standard solution and a sample solution with a concentration range of 0.5-2 g / L; (2) setting the detection wavelength to 210 nm, and after the instrument baseline stabilizes, injecting the standard, the sample to be tested, and the standard in sequence, and calculating the average peak area of ​​the standard solution and the sample solution to be tested respectively; (3) calculating the content of methyl N-chloroformyl-N-[4-(trifluoromethoxy)phenyl]carbamate in the sample to be tested according to the external standard method formula.

[0008] The external standard method for gas chromatography analysis of high-boiling-point samples suffers from poor detection of multiple high-boiling-point components. Introducing an internal standard into the test sample further complicates the analytical procedures and data processing. Liquid chromatography (LC) offers significant advantages for analyzing high-boiling-point, non-volatile, and thermally decomposable organic compounds. However, LC has relatively low column and detection temperatures, making it difficult to separate high-boiling-point components. Furthermore, the mobile phase and sample require pre-treatment for preparation and degassing, complicating the process. All of these factors significantly impact the speed and convenience of analyzing 1,4-cyclohexanediethanol with raw materials and hydrogenation products. Summary of the Invention

[0009] Currently, qualitative and quantitative analysis of 1,4-cyclohexanediethanol (CHDM), dimethyl terephthalate (DMT), the starting hydrogenation feedstock of CHDM, and dimethyl 1,4-cyclohexanedicarboxylate (DMCD), the intermediate hydrogenation product of DMT, is mainly performed using liquid chromatography (LC) or gas chromatography (GC). As mentioned earlier, LC has the disadvantages of low column and detection temperatures, making it difficult to separate high-boiling-point components. In addition, the mobile phase and the sample to be tested must be prepared and degassed, making the operation relatively complex. Therefore, GC is used to analyze 1,4-cyclohexanediethanol, its hydrogenation feedstock, and the intermediate hydrogenation product. Since the preparation of CHDM from DMT is generally a continuous process, the same instrument is often used to analyze the feedstock DMT, the intermediate product DMCD, and the final product CHDM to analyze the reaction process and effect. However, due to the high boiling points of DMT, DMCD, and CHDM, and the existence of cis and trans isomers of CHDM, the current analytical methods have poor analytical detection results for the corresponding components.

[0010] Therefore, there is an urgent need to develop an analytical method that can effectively perform qualitative and quantitative analysis of 1,4-cyclohexanediethanol (CHDM), dimethyl terephthalate (DMT), the starting hydrogenation feedstock of CHDM, and 1,4-cyclohexanedicarboxylate (DMCD), the intermediate hydrogenation product of DMT. Furthermore, it can also perform analytical testing of the cis and trans isomers of 1,4-cyclohexanediethanol. Based on this, the inventors provide a new analytical method for 1,4-cyclohexanediethanol, its hydrogenation feedstock, and the intermediate hydrogenation product of the feedstock.

[0011] In addition, the two-step hydrogenation of DMT to prepare CHDM is a relatively mature process. In the two-step hydrogenation of DMT to prepare CHDM, the inventors found that the DMCD content in the DMCD material obtained in the first step of hydrogenation and the CHDM content in the CHDM material obtained in the second step of hydrogenation were both relatively high. The inventors determined that, according to the analytical method provided by the present invention, the corresponding peak patterns of the corresponding components were determined using the corresponding DMT, DMCD and CHDM standards, thereby determining the peak positions of DMT, DMCD and CHDM. Under the same analytical method, materials with DMT, DMCD and CHDM as the main components can be analyzed simultaneously.

[0012] To achieve the above objectives, the present invention provides an analytical method for one or more sample components selected from 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate, the analytical method comprising:

[0013] Sample pretreatment: The sample is pretreated to obtain a liquid free of mechanical impurities, which is then used as the sample to be tested;

[0014] Test sample determination and analysis: The test sample is injected into a gas chromatograph for detection, and the external standard method is used for qualitative analysis;

[0015] The detection conditions include: the detector is an FID detector, and the FID detector temperature is 295-320℃.

[0016] Through the above technical solution, the present invention has at least the following beneficial effects:

[0017] The analytical method of this invention for 1,4-cyclohexanediethanol and its hydrogenation feedstock (dimethyl terephthalate) and the intermediate product of feedstock hydrogenation (dimethyl 1,4-cyclohexanedicarboxylate) employs gas chromatography to simultaneously and effectively perform qualitative and quantitative analysis on 1,4-cyclohexanediethanol and various feedstocks and feedstock hydrogenation products, including dimethyl 1,4-cyclohexanedicarboxylate, dimethyl terephthalate, methanol, and solvents. It can also achieve the analytical testing of cis and trans isomers of 1,4-cyclohexanediethanol. Under the same gas chromatographic analysis conditions, only one injection is required to simultaneously obtain the content of one or more components in the sample, including but not limited to 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, dimethyl terephthalate, and methanol. Its determination method is simple, reproducible, sensitive, stable, easy to operate, and fast. It can meet the analysis requirements of 1,4-cyclohexanediethanol and its raw materials and hydrogenation products of raw materials, or samples containing or partially containing similar components. It eliminates the tedious operation of selecting and adding internal standards. It can also be used for the quantitative analysis of other similar samples. It has a positive promoting effect on the production and use of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate products. Attached Figure Description

[0018] Figure 1 This is a gas chromatogram of the component content determination of the 1,4-cyclohexanediethanol (CHDM) product in Example 1;

[0019] Figure 2 This is a gas chromatogram of the component content determination of 1,4-cyclohexanediethanol (CHDM) product in Example 2;

[0020] Figure 3 This is a gas chromatogram showing the results of the determination of the content of each component in the two-stage hydrogenation product of dimethyl terephthalate (DMT) in Example 3;

[0021] Figure 4 This is a gas chromatographic graph showing the content of each component in the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product in Example 7.

[0022] Figure 5This is a gas chromatographic graph showing the content of each component in the first hydrogenation product of dimethyl terephthalate (DMT) in Example 8;

[0023] Figure 6 This is a gas chromatographic graph showing the content of each component in the solution containing dimethyl terephthalate (DMT) and dimethyl 1,4-cyclohexanedicarboxylate (DMCD) in Example 11. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] This invention provides an analytical method for one or more sample components selected from 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate. The analytical method includes:

[0026] Sample pretreatment: The sample is pretreated to obtain a liquid free of mechanical impurities, which is then used as the sample to be tested;

[0027] Test sample determination and analysis: The test sample is injected into a gas chromatograph for detection, and the external standard method is used for qualitative analysis;

[0028] The detection conditions include: the detector is an FID detector, and the FID detector temperature is 295-320℃.

[0029] The analytical method of this invention can simultaneously determine the content of one or more components, including but not limited to 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate, in the sample under the same gas chromatographic analysis conditions with only one injection. The method is simple, reproducible, accurate, sensitive, and stable. It is easy to operate and fast, and can meet the analysis requirements of 1,4-cyclohexanediethanol and its hydrogenation feedstock and intermediate products, eliminating the cumbersome operation of selecting and adding internal standards.

[0030] According to a preferred embodiment of the present invention, the area normalization method is used for quantification of the sample under test. The aforementioned embodiment demonstrates that the area normalization method can be used to quantitatively analyze materials with DMT, DMCD, and CHDM as the main components simultaneously under the same analytical method, and can also qualitatively and quantitatively analyze cis and trans isomers in CHDM materials.

[0031] The specific method of area normalization in this invention is a method well known to those skilled in the art, and will not be elaborated upon here.

[0032] According to a preferred embodiment of the present invention, the detection conditions include: an FID detector temperature of 295-310°C, for example, 295°C, 298°C, 300°C, 305°C, or 310°C. The analytical method of the aforementioned embodiment has better detection stability.

[0033] In this invention, when performing gas chromatography detection, the sample needs to be completely vaporized when it enters the gas chromatograph injection port. As long as the purpose of this invention can be achieved, the injection port temperature is not particularly limited. Preferably, the detection conditions include an injection port temperature of 250-295℃, for example, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 290℃, and preferably 275-290℃.

[0034] According to a preferred embodiment of the present invention, the detection conditions include: a column temperature programmable temperature rise: an initial temperature of 105-150°C (e.g., 105°C, 110°C, 115°C, 120°C, 130°C, 135°C, 140°C, or 150°C) is maintained for 1-10 minutes (e.g., 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes), followed by a temperature rise of 5-30°C / min (e.g., 5°C / min, 8°C / min, 10°C / min, 12°C / min, 15°C / min, 18°C / min, or 20°C / min) to 250-295°C (e.g., 250°C, 260°C, 270°C, 280°C, 290°C, or 295°C) and maintained for 20-50 minutes (e.g., 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, or 50 minutes). The analytical method described above provides accurate, sensitive, and stable results when analyzing at least one sample component containing 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0035] According to a more preferred embodiment of the present invention, the detection conditions include: a column temperature program: an initial temperature of 110-130°C, held for 2-5 minutes, then increased to 275-290°C at a rate of 10-20°C / min and held for 25-40 minutes. The analytical method described above provides more accurate, more sensitive, and more stable results when analyzing sample components containing at least one of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0036] According to the present invention, in gas chromatography, the sample is separated in a chromatographic column, and preferably, the detection conditions include: the chromatographic separation column is a capillary chromatographic column.

[0037] According to a preferred embodiment of the present invention, the detection conditions include: the length of the chromatographic separation column is 15-60 m. For example, it can be 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 50 m, 55 m, 60 m, or any combination of two of the above values, preferably 30-60 m. The analytical method of the aforementioned embodiment provides more accurate, more sensitive, and better stable results when analyzing samples containing at least one of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0038] According to a preferred embodiment of the present invention, the detection conditions include: the inner diameter of the chromatographic separation column is 0.25-0.55 mm. For example, it is 0.25 mm, 0.3 mm, 0.32 mm, 0.35 mm, 0.4 mm, 0.5 mm, 0.55 mm, or a range of any two of the above values, preferably 0.3-0.35 mm.

[0039] According to the present invention, preferably, the capillary column is selected from weakly polar capillary columns. The analytical method of the foregoing embodiments provides more accurate, more sensitive, and more stable results when analyzing sample components containing at least one of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0040] According to the present invention, the stationary phase in the chromatographic column is a phase that retains the sample, and its main function is to separate the components in the sample as they pass through the chromatographic column. Preferably, the stationary phase on the inner wall of the weakly polar capillary column is 5 wt% phenyl-95 wt% methyl polysiloxane or 5.5 wt% phenyl-94.5 wt% dimethyl polysiloxane, more preferably 5 wt% phenyl-95 wt% methyl polysiloxane. The analytical method of the foregoing embodiments provides more accurate, more sensitive, and more stable results when analyzing sample components containing at least one of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0041] According to a preferred embodiment of the present invention, the thickness of the stationary phase on the inner wall of the weakly polar capillary column is 0.25-0.5 μm, for example, 0.25 μm, 0.33 μm, 0.42 μm, 0.5 μm, or any combination of two of the above values, preferably 0.25-0.33 μm.

[0042] According to a preferred embodiment of the present invention, the detection conditions include a split ratio of 60:1-200:1, for example, 60:1, 80:1, 100:1, 110:1, 120:1, 140:1, 160:1, 180:1, 200:1, or a range consisting of any two of the above ratios, preferably 80:1-120:1.

[0043] According to the present invention, when analyzing samples using gas chromatography, a carrier gas is required to carry the sample into the gas chromatograph. As long as the purpose of the present invention can be achieved, the specific type of carrier gas is not particularly limited. Generally, nitrogen is used. The preferred flow rate of the carrier gas is 1-10 ml / min, for example, 1 ml / min, 3 ml / min, 3 ml / min, 4 ml / min, 5 ml / min, 6 ml / min, 8 ml / min, 10 ml / min, and preferably 2-6 ml / min.

[0044] According to the present invention, when analyzing samples using gas chromatography, a fuel gas and an oxidizing gas are required to form a flame and extinguish it inside the detector. Generally, the fuel gas is hydrogen and the oxidizing gas is air. Preferably, the detection conditions include: an air flow rate of 200-600 ml / min, for example, 200 ml / min, 250 ml / min, 300 ml / min, 320 ml / min, 330 ml / min, 340 ml / min, 350 ml / min, 360 ml / min, 380 ml / min, 400 ml / min, 420 ml / min, 450 ml / min, 550 ml / min, or 600 ml / min, preferably 300-420 ml / min; preferably, the detection conditions include: a hydrogen flow rate of 40-80 ml / min, for example, 40 ml / min, 50 ml / min, 60 ml / min, 65 ml / min, 70 ml / min, or 80 ml / min, preferably 60-70 ml / min.

[0045] According to the present invention, as long as the purpose of the present invention can be achieved, there is no special limitation on the injection volume when performing gas chromatography analysis. Preferably, the detection conditions include: the injection volume is 0.2-0.5 μL, more preferably 0.2-0.3 μL.

[0046] As mentioned above, 1,4-cyclohexanediethanol (CHDM) is mainly produced using a two-step hydrogenation route of dimethyl terephthalate (DMT). In the first step, the benzene ring of DMT is hydrogenated to form dimethyl 1,4-cyclohexanedicarboxylate (DMCD), and in the second step, the DMCD ester is hydrogenated to generate CHDM. According to the analytical method of the present invention, samples whose main components are dimethyl terephthalate (DMT), dimethyl 1,4-cyclohexanedicarboxylate (DMCD), or 1,4-cyclohexanediethanol (CHDM) can be detected. In the present invention, the sample is pretreated to obtain a liquid free of mechanical impurities as the sample to be tested.

[0047] The main components of the sample in this invention are based on a comparison of the contents of 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate.

[0048] According to a preferred embodiment of the present invention, when the main component of the sample is 1,4-cyclohexanediethanol: the source of the sample includes at least one of the processes of production, use and recycling of 1,4-cyclohexanediethanol.

[0049] In this invention, the following can be listed as 1,4-cyclohexanediethanol in the production, use and recycling process: 1,4-cyclohexanediethanol products, hydrogenated products containing 1,4-cyclohexanediethanol as the main component obtained by one-step hydrogenation of dimethyl 1,4-cyclohexanedicarboxylate or two-step hydrogenation of dimethyl terephthalate as the main component, and materials containing 1,4-cyclohexanediethanol as the main component in the refining and purification process of the above hydrogenated products.

[0050] According to a preferred embodiment of the present invention, when the main component of the sample is 1,4-cyclohexanediethanol, the sample pretreatment method includes: heating the sample to 30-100°C to completely melt it to obtain the sample to be tested, preferably to completely melt it at 60-80°C.

[0051] According to a preferred embodiment of the present invention, when the main component of the sample is 1,4-cyclohexanediethanol, the sample pretreatment method includes: dissolving the sample in a solvent to obtain the sample to be tested, wherein the solvent is selected from monohydric alcohols and / or dihydric alcohols that are liquid at room temperature, preferably selected from at least one of methanol, ethanol, and ethylene glycol, and more preferably ethanol; preferably, the content of the sample in the sample to be tested is not particularly limited, as long as it can be ensured that the sample does not crystallize and precipitate, for example, the content of the sample in the sample to be tested is 10-80 wt%, specifically such as 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, and 80 wt%.

[0052] According to a preferred embodiment of the present invention, when the main component of the sample is dimethyl 1,4-cyclohexanedicarboxylate: the source of the sample includes at least one of the processes of production, use and recycling of dimethyl 1,4-cyclohexanedicarboxylate.

[0053] In this invention, at least one of the following can be listed in the production, use, and recycling processes: dimethyl 1,4-cyclohexanedicarboxylate products, hydrogenated products containing dimethyl 1,4-cyclohexanedicarboxylate as the main component obtained by one-step hydrogenation of dimethyl terephthalate as a raw material, and materials containing dimethyl 1,4-cyclohexanedicarboxylate as the main component during the refining and purification process of the above hydrogenated products.

[0054] According to a preferred embodiment of the present invention, when the main component of the sample is dimethyl 1,4-cyclohexanedicarboxylate, the sample pretreatment method includes: completely melting the sample at 30-100°C to obtain the sample to be tested, preferably completely melting at 60-80°C.

[0055] In this invention, "complete melting" refers to processing the sample into a uniform, transparent liquid free of mechanical impurities, ensuring that the sample does not crystallize or precipitate at room temperature.

[0056] According to a preferred embodiment of the present invention, when the main component of the sample is dimethyl terephthalate: the source of the sample includes at least one of the processes of production, use and recycling of dimethyl terephthalate.

[0057] In this invention, at least one type of dimethyl terephthalate that can be listed in the production, use and recycling process includes dimethyl terephthalate products, hydrogenated products that still contain dimethyl terephthalate components obtained by hydrogenation of dimethyl terephthalate as a raw material, and materials containing dimethyl terephthalate as the main component in the refining and purification process.

[0058] According to a preferred embodiment of the present invention, when the main component of the sample is dimethyl terephthalate, the sample pretreatment method includes: contacting the sample with a solvent to obtain a sample to be tested, wherein the solvent is selected from dimethyl 1,4-cyclohexanedicarboxylate and / or ethyl acetate, preferably dimethyl 1,4-cyclohexanedicarboxylate; wherein the conditions for contacting the sample with the solvent are not particularly limited, as long as the sample can be completely dissolved in the solvent to obtain a liquid free of mechanical impurities, for example, the contact temperature is 60-140°C, preferably 80-140°C; wherein the content of the sample in the sample to be tested can be determined as needed, preferably, the content of the sample in the sample to be tested is 0.1wt%-90wt%, for example, 0.1wt%, 1wt%, 5wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, preferably 0.1-50wt%. The analytical method under the aforementioned embodiment has better repeatability and accuracy.

[0059] The present invention will be described in detail below through embodiments.

[0060] Example 1

[0061] A certain amount of ethanol was added to a sample of 1,4-cyclohexanediethanol to dissolve the sample, preparing a homogeneous, transparent solution free of mechanical impurities. The content of 1,4-cyclohexanediethanol in the solution was approximately 57 wt%. The sample was directly injected into a gas chromatograph at room temperature using an injector. Gas chromatography was used to analyze the sample, with an SE-54 gas chromatograph capillary column (50 m × 0.32 mm × 0.25 μm) as the analytical column. The injection port temperature was 280 °C, and the FID detector temperature was 300 °C. The column temperature was maintained at 120 °C for 3 min, then increased to 280 °C at a rate of 15 °C / min and maintained for 30 min. Nitrogen was used as the carrier gas at a flow rate of 4 ml / min. The split ratio was 100:1. The hydrogen flow rate was 60 ml / min, and the air flow rate was 400 ml / min. The injection volume was 0.3 μL, and external standard method was used for qualitative analysis.

[0062] The gas chromatographic results of the first determination of the 1,4-cyclohexanediethanol (CHDM) product component content were obtained by two parallel determinations, after subtracting the peak of the solvent ethanol. Figure 1 The peak positions and contents (peak area (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method, and the results are shown in Table 1.

[0063] Example 2

[0064] The method is the same as in Example 1, except that the injection volume is 0.2 μL and external standard method is used for characterization.

[0065] The determination was performed twice in parallel. After subtracting the peak from the solvent ethanol, the results of the first determination of the component content of 1,4-cyclohexanediethanol (CHDM) are shown below. Figure 2 The peak positions and contents (peak area (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method, and the results are shown in Table 1.

[0066] Example 3

[0067] The sample derived from the second-stage hydrogenation product of dimethyl terephthalate (DMT) is a sample containing 1,4-cyclohexanediethanol (CHDM) as the main component. The sample was heated to 80°C until completely melted, resulting in a homogeneous, transparent liquid free of mechanical impurities. This liquid was then injected into a gas chromatograph (GC) using an SE-54 capillary column (50 m × 0.32 mm × 0.25 μm). The injection port temperature was 280°C, and the FID detector temperature was 300°C. The column temperature was maintained at 120°C for 3 min, then increased to 280°C at a rate of 15°C / min and maintained for 30 min. Nitrogen was used as the carrier gas at a flow rate of 4 ml / min; the split ratio was 100:1; the hydrogen flow rate was 60 ml / min, and the air flow rate was 400 ml / min. The injection volume was 0.2 μL, and external standard analysis was used.

[0068] The gas chromatographic results of the first determination of the components of the two-stage hydrogenation products of dimethyl terephthalate (DMT) were obtained by three parallel determinations. Figure 3 The peak positions and contents (peak area (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method, and the results are shown in Table 1.

[0069] Example 4

[0070] The method according to Example 1 differs in that:

[0071] The injection port temperature was 290℃, and the FID detector temperature was 310℃. The column temperature was 120℃ for 2 min, then increased to 290℃ at a rate of 15℃ / min and held for 25 min. Nitrogen was used as the carrier gas with a flow rate of 5 ml / min. The split ratio was 80:1. The hydrogen flow rate was 50 ml / min, and the air flow rate was 400 ml / min.

[0072] The rest is the same as in Example 1.

[0073] The peaks of the solvent ethanol were subtracted from the three parallel determinations. The peak positions and contents (peak areas (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method. The results are shown in Table 1.

[0074] Example 5

[0075] The method according to Example 1 differs in that:

[0076] After maintaining the column temperature at 160℃ for 3 minutes, the temperature was increased to 260℃ at a rate of 14℃ / min and maintained for 30 minutes.

[0077] The rest is the same as in Example 1.

[0078] The peaks of the solvent ethanol were subtracted from the three parallel determinations. The peak positions and contents (peak areas (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method. The results are shown in Table 1.

[0079] Example 6

[0080] The method of Example 3 differs in that:

[0081] The sample from the second-stage hydrogenation product of dimethyl terephthalate was dissolved in ethanol to prepare a homogeneous, transparent solution free of mechanical impurities. The sample content in the solution was 60 wt%. The solution was then directly injected into the gas chromatograph using an injector at room temperature.

[0082] The peaks of the solvent ethanol were subtracted from the three parallel determinations. The peak positions and contents (peak areas (%)) of each component in the 1,4-cyclohexanediethanol (CHDM) product were determined by external standard method. The results are shown in Table 1.

[0083] Example 7

[0084] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) was heated to 60°C until completely melted, resulting in a homogeneous, transparent liquid free of mechanical impurities. This liquid was then directly injected into a gas chromatograph using an injector. Gas chromatography was employed to analyze the sample using an SE-54 capillary column (50m × 0.32mm × 0.25μm). The injection port temperature was 280°C, and the FID detector temperature was 300°C. The column temperature was maintained at 120°C for 3 minutes, then increased to 280°C at a rate of 15°C / min and maintained for 30 minutes. Nitrogen was used as the carrier gas at a flow rate of 4 ml / min, with a split ratio of 100:1. Hydrogen flow rate was 60 ml / min, and air flow rate was 400 ml / min. The injection volume was 0.2 μL, and external standard analysis was used for qualitative analysis.

[0085] The results of the gas chromatography determination of the contents of each component of the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product in the first step were obtained in triplicate. Figure 4 The peak positions and contents (peak area (%)) of each component in the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product were determined by external standard method, and the results are shown in Table 2.

[0086] Example 8

[0087] The primary hydrogenation product of dimethyl terephthalate (DMT), namely a sample containing dimethyl 1,4-cyclohexanedicarboxylate (DMCD) as the main component, was heated to 55°C until completely melted, resulting in a homogeneous, transparent liquid free of mechanical impurities. This liquid was then directly injected into a gas chromatograph using an injector. Gas chromatography analysis was performed using an SE-54 capillary column (50m × 0.32mm × 0.25μm). The injection port temperature was 280°C, and the FID detector temperature was 300°C. The column temperature was maintained at 120°C for 3 min, then increased to 280°C at a rate of 15°C / min and maintained for 30 min. Nitrogen was used as the carrier gas at a flow rate of 4 ml / min. The split ratio was 100:1. The hydrogen flow rate was 60 ml / min, and the air flow rate was 400 ml / min. The injection volume was 0.5 μL, and external standard analysis was used for characterization.

[0088] The results of the gas chromatography determination of the components of the first hydrogenation product of dimethyl terephthalate (DMT) were obtained by three parallel determinations. Figure 5 The peak positions and contents (peak area (%)) of each component in the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product were determined by external standard method, and the results are shown in Table 2.

[0089] Example 9

[0090] The method according to Example 7 differs in that:

[0091] Dimethyl 1,4-cyclohexanedicarboxylate (DMCD) was dissolved in acetone at 50°C to prepare a homogeneous, transparent solution free of mechanical impurities with a sample content of 60 wt%. The solution was then injected into a gas chromatograph using an injector.

[0092] The rest is the same as in Example 7.

[0093] The peaks of the solvent acetone were subtracted from the three parallel determinations. The peak positions and contents (peak areas (%)) of each component in the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product were determined by external standard method. The results are shown in Table 2.

[0094] Example 10

[0095] The method according to Example 7 differs in that:

[0096] After holding the column temperature at 100℃ for 5 minutes, the temperature was increased to 140℃ at a rate of 4℃ / min and held for 5 minutes. Finally, the temperature was increased to 180℃ at a rate of 10℃ / min and held for 2 minutes.

[0097] The rest is the same as in Example 7.

[0098] The peak positions and contents (peak area (%)) of each component in the dimethyl 1,4-cyclohexanedicarboxylate (DMCD) product were determined by external standard method in three parallel determinations. The results are shown in Table 2.

[0099] Example 11

[0100] A certain amount of sample containing dimethyl terephthalate (DMT) as the main component was dissolved completely by adding a certain amount of dimethyl 1,4-cyclohexanedicarboxylate as a solvent and heating to 95°C to prepare a homogeneous, transparent solution free of mechanical impurities. The sample content in the solution was 10 wt%. The sample was injected into a gas chromatograph using an injector. Gas chromatography was used to analyze the sample. An SE-54 gas chromatograph capillary column (50 m × 0.32 mm × 0.25 μm) was used as the analytical column. The injection port temperature was 280°C and the FID detector temperature was 300°C. The column temperature was maintained at 120°C for 3 min, then increased to 280°C at a rate of 15°C / min and maintained for 30 min. Nitrogen was used as the carrier gas with a flow rate of 4 ml / min and a split ratio of 100:1. The hydrogen flow rate was 60 ml / min and the air flow rate was 400 ml / min. The injection volume was 0.3 μL, and external standard method was used for qualitative analysis.

[0101] The gas chromatographic determination of the components in the solution containing dimethyl terephthalate (DMT) and dimethyl 1,4-cyclohexanedicarboxylate (DMCD) was performed in triplicate. The results are shown in the table below. Figure 6 The peak positions and contents (peak area (%)) of each component in the solution were determined by external standard method, and the results are shown in Table 3.

[0102] The purity of dimethyl terephthalate (DMT) can be obtained by recalculating the content of dimethyl 1,4-cyclohexanedicarboxylate (DMCD) in the analysis results.

[0103] Example 12

[0104] The method according to Example 11 differs in that:

[0105] The injection port temperature was 290℃, and the FID detector temperature was 310℃. The column temperature was 120℃ for 2 min, then increased to 290℃ at a rate of 15℃ / min and held for 25 min. Nitrogen was used as the carrier gas with a flow rate of 5 ml / min. The split ratio was 80:1. The hydrogen flow rate was 50 ml / min, and the air flow rate was 400 ml / min.

[0106] The rest is the same as in Example 11.

[0107] The determination was performed in three parallel trials. The peak positions and contents (peak area (%)) of each component in the solution were determined by external standard method. The results are shown in Table 3.

[0108] Example 13

[0109] The method according to Example 11 differs in that:

[0110] After holding the column temperature at 100℃ for 5 minutes, the temperature was increased to 140℃ at a rate of 4℃ / min and held for 5 minutes. Finally, the temperature was increased to 180℃ at a rate of 10℃ / min and held for 2 minutes.

[0111] The rest is the same as in Example 11.

[0112] The determination was performed in three parallel trials. The peak positions and contents (peak area (%)) of each component in the solution were determined by external standard method. The results are shown in Table 3.

[0113] Comparative Example 1

[0114] The method according to Example 1 differs in that:

[0115] The injection port temperature was 280℃, and the FID detector temperature was 280℃. The column temperature was 160℃ for 5 minutes, then increased to 260℃ at a rate of 14℃ / min and held for 30 minutes.

[0116] The results were obtained by performing three parallel determinations and subtracting the peak of the solvent ethanol. The relative standard deviation (RSD) of the trans CHDM was 0.38% and that of the cis CHDM was 1.24%.

[0117] Comparative Example 2

[0118] The method according to Example 7 differs in that:

[0119] The injection port temperature was 280℃, and the FID detector temperature was 200℃. After holding the column temperature at 100℃ for 5 minutes, it was increased to 140℃ at a rate of 4℃ / min and held for 5 minutes. Finally, it was increased to 180℃ at a rate of 10℃ / min and held for 2 minutes.

[0120] The results were measured in three parallel measurements, and the relative standard deviation (RSD) was 0.84%.

[0121] Table 1

[0122]

[0123]

[0124]

[0125] Table 2

[0126]

[0127] Table 3

[0128]

[0129]

[0130] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An analytical method for one or more sample components comprising 1,4-cyclohexanediethanol, dimethyl 1,4-cyclohexanedicarboxylate, and dimethyl terephthalate, characterized in that, The analytical method includes: Sample pretreatment: The sample is pretreated to obtain a liquid free of mechanical impurities, which is then used as the sample to be tested; Test sample determination and analysis: The test sample is injected into a gas chromatograph for detection, and the external standard method is used for qualitative analysis; The detection conditions include: the detector is an FID detector, and the FID detector temperature is 295-320℃.

2. The analytical method according to claim 1, characterized in that, The area normalization method was used for quantification of the sample during analysis. and / or The testing conditions include: The temperature of the FID detector is 295-310℃; and / or The injection port temperature is 250-295℃.

3. The analytical method according to claim 1, characterized in that, The testing conditions include: Column temperature program: Initial temperature 105-150℃, hold for 1-10 min, then increase to 250-295℃ at 5-30℃ / min and hold for 20-50 min.

4. The analytical method according to claim 1, characterized in that, The testing conditions include: The chromatographic separation column is a capillary column; and / or The length of the chromatographic separation column is 15-60 m; and / or The inner diameter of the chromatographic separation column is 0.25-0.55 mm.

5. The analytical method according to claim 4, characterized in that, The testing conditions include: The capillary column is selected from weakly polar capillary columns.

6. The analytical method according to claim 5, characterized in that, The stationary phase on the inner wall of the weakly polar capillary column is 5 wt% phenyl-95 wt% methyl polysiloxane or 5.5 wt% phenyl-94.5 wt% dimethyl polysiloxane; and / or The thickness of the stationary phase on the inner wall of the weakly polar capillary column is 0.25-0.5 μm.

7. The analytical method according to claim 1, characterized in that, The testing conditions include: The split ratio is 60:1-200:1; and / or The carrier gas is nitrogen; and / or The carrier gas flow rate is 1-10 ml / min; and / or Airflow rate is 200-600 ml / min; and / or Hydrogen flow rate is 40-80 ml / min; and / or The injection volume is 0.2-0.5 μL.

8. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is 1,4-cyclohexanediethanol: the source of the sample includes at least one of the production, use and recycling processes of 1,4-cyclohexanediethanol.

9. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is 1,4-cyclohexanediethanol, the sample pretreatment method includes: heating the sample to 30-100℃ to completely melt it to obtain the sample to be tested.

10. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is 1,4-cyclohexanediethanol, the sample pretreatment method includes: dissolving the sample in a solvent to obtain the sample to be tested, wherein the solvent is selected from monohydric alcohols and / or dihydric alcohols that are liquid at room temperature.

11. The analytical method according to claim 10, characterized in that, The solvent is selected from at least one of methanol, ethanol, and ethylene glycol; and / or The content of the sample to be tested is 10-80 wt%.

12. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is dimethyl 1,4-cyclohexanedicarboxylate: the source of the sample includes at least one of the processes of production, use and recycling of dimethyl 1,4-cyclohexanedicarboxylate.

13. The analytical method according to claim 12, characterized in that, When the main component of the sample is dimethyl 1,4-cyclohexanedicarboxylate, the sample pretreatment method includes: completely melting the sample at 30-100℃ to obtain the sample to be tested.

14. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is dimethyl terephthalate: the source of the sample includes at least one of the processes of production, use and recycling of dimethyl terephthalate.

15. The analytical method according to any one of claims 1-7, characterized in that, When the main component of the sample is dimethyl terephthalate, the sample pretreatment method includes: contacting the sample with a solvent to obtain the sample to be tested, wherein the solvent is selected from dimethyl 1,4-cyclohexanedicarboxylate and / or ethyl acetate.

16. The analytical method according to claim 15, characterized in that, The solvent is selected from dimethyl 1,4-cyclohexanedicarboxylate; and / or The temperature of the contact is 60-140°C; and / or The content of the sample in the test sample is 0.1-90 wt%.

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