A method for detecting volatile gas based on gas chromatography-ion mobility spectrometry

Abstract

The application provides a volatile gas detection method based on gas chromatography-ion mobility spectrometry, and belongs to the volatile gas detection field. The method comprises the following steps: using a MOFs functionalized adsorption tube to selectively capture volatile gas generated in petroleum chemical industry; the MOFs functionalized adsorption tube is internally sequentially filled with a silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a mixed layer of a poly 2,6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and a carbon molecular sieve adsorbent; through a two-stage thermal desorption procedure, the captured volatile gas is desorbed from the adsorption tube; and the desorbed volatile gas is introduced into a gas chromatography-ion mobility spectrometry instrument for volatile gas content determination. Thus, the efficiency and accuracy of the content detection of the volatile gas in the petroleum chemical industry are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of volatile gas detection, and particularly relates to a volatile gas detection method based on gas chromatography-ion mobility spectrometry. BACKGROUND

[0002] In many industrial fields such as petrochemical industry and in the category of environmental monitoring, accurate detection of volatile gas is of great importance. The production process of petrochemical industry is complex, and a large amount of volatile gas including benzene series, olefins and sulfur compounds will be generated. These gases not only pollute the environment, such as benzene series, which are common air pollutants, can cause air quality to decline and damage the ecological environment, but also have great harm to human health, for example, long-term exposure to low-concentration benzene series may cause serious diseases such as leukemia, and sulfur compounds have irritating odor, which can stimulate the respiratory tract and damage the respiratory system of human body. Therefore, effective detection of these volatile gases is of great significance to environmental protection, safety production and human health protection.

[0003] There are many traditional methods for detecting volatile gas, but each has obvious defects. For example, although gas chromatography-mass spectrometry (GC-MS) technology has high sensitivity, it has large equipment volume, high price, strict requirements for detection environment and operating personnel, long time for analyzing samples, and is difficult to use in scenes requiring rapid and on-site detection. Proton transfer reaction-mass spectrometry (PTR-MS) is also complex and costly, and performs poorly in selective detection of specific volatile gases. Although the fluorescence probe method responds to certain specific substances, its application range is narrow and it cannot comprehensively detect a variety of mixed volatile gases. Although the photoacoustic spectrometer can detect gases, it has the problem of insufficient detection accuracy and limited detection capability for low-concentration volatile gases. Ion mobility spectrometry (IMS) has unique advantages as an analysis technology. It can characterize the properties of ion substances according to the migration speed of different gas-phase ions in an electric field, can work at normal pressure, has simple device structure, high sensitivity, and detection limit can reach ng or even pg level, and is suitable for detection of trace volatile organic compounds. However, IMS also has obvious shortcomings. Its separation ability is poor, and when facing complex matrix samples, it is difficult to effectively separate different volatile gases, thereby affecting the accuracy of the detection results. Gas chromatography (GC) has good separation ability and can separate different compounds in the sample based on the differences in adsorption and desorption characteristics in the chromatographic column. However, the detection limit of GC is not low enough, and it has difficulty in detecting low-concentration volatile gases.

[0004] In view of this, gas chromatography-ion mobility spectrometry (GC-IMS) technology, which combines the high separation ability of gas chromatography with the high sensitivity and rapid detection advantages of ion mobility spectrometry, has emerged. However, when GC-IMS technology is actually applied to the detection of volatile gases in the petrochemical industry and other fields, it still faces many challenges. On the one hand, existing adsorbent materials are difficult to achieve efficient and selective capture of the complex and diverse volatile gases in the petrochemical industry, which limits the accuracy and sensitivity of detection. On the other hand, the thermal desorption process is not precise and efficient enough, and problems such as peak overlap may occur, affecting the separation and quantitative analysis of different volatile gases. Moreover, some parameter settings of the GC-IMS instrument need to be optimized to better adapt to the detection needs of complex volatile gases. Therefore, there is an urgent need to develop a method that can overcome the above problems and achieve efficient and accurate detection of volatile gases in the petrochemical industry. SUMMARY

[0005] The present application provides a method for detecting volatile gases based on gas chromatography-ion mobility spectrometry, to solve the technical problem of how to improve the efficiency and accuracy of content detection of volatile gases in the petrochemical industry.

[0006] The present application provides a method for detecting volatile gases based on gas chromatography-ion mobility spectrometry, which comprises:

[0007] The MOFs functionalized adsorption tube is used to selectively capture volatile gases generated in the petrochemical industry; the MOFs functionalized adsorption tube is sequentially filled with a silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a mixed layer of poly2,6-diphenyl ether / graphitized carbon black composite adsorbent and carbon molecular sieve adsorbent;

[0008] The captured volatile gases are desorbed from the adsorption tube through a two-stage thermal desorption process;

[0009] The desorbed volatile gases are introduced into a gas chromatography-ion mobility spectrometry instrument for content determination of volatile gases.

[0010] Optionally, the particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 80-120 mg;

[0011] The particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 130-170 mg;

[0012] The mixing ratio of the poly2,6-diphenyl ether / graphitized carbon black composite adsorbent and the carbon molecular sieve adsorbent is 1:(0.8-1.2), and the total filling amount is 180-220 mg.

[0013] Optionally, the silver ion modified UIO-66 metal organic framework has Ag + The loading amount is 5-15wt% of the mass of UIO-66.

[0014] Optionally, the preparation method of the poly-2,6-diphenyl-p-phenylene oxide / graphitized carbon black composite adsorbent comprises:

[0015] The graphitized carbon black is reacted with mixed acid at 80℃ for 6h, and after washing and drying, a modified GCB containing carboxyl / hydroxyl is obtained;

[0016] The modified GCB is dispersed in a toluene solution of 2,6-diphenylphenol monomer, and a Cu + / amine complex catalyst formed by adding cuprous chloride and N,N-dimethyl-n-butylamine is added, and then oxygen is introduced to react at 75℃ for 8h to obtain a reaction solution;

[0017] After the reaction solution is precipitated and centrifuged with methanol and then washed with methanol and acetone, a core-shell composite poly-2,6-diphenyl-p-phenylene oxide / graphitized carbon black composite adsorbent is obtained.

[0018] Optionally, the amount of mixed acid is 100mL of mixed acid per 10g of graphitized carbon black, and the mixed acid is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1;

[0019] The mass ratio of the cuprous chloride to the N,N-dimethyl-n-butylamine is 1:2.4;

[0020] The mass ratio of the modified GCB to the 2,6-diphenylphenol monomer is 1:2.5.

[0021] Optionally, the MOFs functionalized adsorption tube is made of stainless steel, has an inner diameter of 6-8mm, and a length of 8-12cm.

[0022] Optionally, in the two-stage thermal desorption process, the first-stage desorption temperature is 70-90℃, the flow rate of high-purity hydrogen carrier gas is 0.8-1.2mL / min, and the duration time is 1.5-2.5min, which is used for desorbing C2-C5 light hydrocarbons; the second-stage desorption temperature is 240-260℃, the flow rate of high-purity hydrogen carrier gas is 1.8-2.2mL / min, and the duration time is 4-6min, which is used for desorbing benzene series and sulfur-containing compounds.

[0023] Optionally, in the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part uses an ionic liquid capillary column as the main column, which has a length of 25-35m, an inner diameter of 0.2-0.3mm, and a film thickness of 0.15-0.25μm; and is equipped with an Al2O3 / KCl PLOT pre-column, which has a length of 8-12m and an inner diameter of 0.3-0.4mm.

[0024] Optionally, in the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part uses a 10 keV X-ray source as an ionization source, the migration tube length is 8-12 cm, the front-stage electric field gradient is 180-220 V / cm, the rear-stage electric field gradient is 380-420 V / cm, the drift gas is high-purity nitrogen, and the flow rate is 280-320 mL / min.

[0025] Optionally, the volatile gas includes benzene series, olefins, and sulfur-containing compounds.

[0026] Compared with the prior art, the above technical solution provided in the embodiments of the present application has the following advantages:

[0027] The present application provides a detection method for volatile gas based on gas chromatography-ion mobility spectrometry, which comprises: using a MOFs functionalized adsorption tube to selectively capture volatile gas generated in petroleum chemical industry; the MOFs functionalized adsorption tube is internally filled with a mixed layer of silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a poly2,6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and carbon molecular sieve adsorbent in sequence; through a two-stage thermal desorption procedure, the captured volatile gas is desorbed from the adsorption tube; and the desorbed volatile gas is introduced into a gas chromatography-ion mobility spectrometry instrument for content determination of the volatile gas.

[0028] Firstly, the MOFs functionalized adsorption tube adopts three layers of gradient adsorption materials, the silver ion modified UIO-66 selectively captures olefins through the π-complexation of Ag⁺ and olefins; the copper benzene tricarboxylate has strong adsorption capacity for polar sulfur-containing compounds; and the composite adsorbent mixed layer captures neutral / weakly polar substances such as benzene series. The layered selective adsorption reduces interference adsorption, improves the specificity of target capture, and lays a foundation for accurate detection.

[0029] Secondly, the two-stage thermal desorption optimizes the detection efficiency, and the target substances with different boiling points / adsorption strengths are desorbed in stages, the light hydrocarbon (C2-C5) is quickly desorbed at low temperature to avoid decomposition of components caused by high temperature, and the benzene series and sulfur-containing compounds are completely desorbed at high temperature. The graded desorption shortens the single analysis time, while ensuring complete release of the target substances, and improves the detection efficiency and recovery rate.

[0030] Thirdly, the combined technology enhances the separation and qualitative ability, the gas chromatography realizes high-efficiency separation of complex components, the ion mobility spectrometry further distinguishes isomers through ion mobility difference, and the combination of the two greatly improves the separation degree and qualitative accuracy of target substances in a complex system, and reduces misjudgment.

[0031] Thus, the efficiency and accuracy of content detection of volatile gas in petroleum chemical industry are improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate preferred embodiments of the application and, together with the description, serve to explain the principles of the application.

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the field, other drawings can also be obtained based on these drawings without any creative effort.

[0034] Figure 1 A flowchart of a volatile gas detection method based on gas chromatography-ion mobility spectrometry provided by the embodiments of the present application. DETAILED DESCRIPTION

[0035] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of protection of the present application.

[0036] Unless otherwise specifically indicated, all the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing methods.

[0037] Figure 1 A flowchart of a volatile gas detection method based on gas chromatography-ion mobility spectrometry provided by the embodiments of the present application.

[0038] As shown in the formula (I), the present application provides a volatile gas detection method based on gas chromatography-ion mobility spectrometry, which comprises: Figure 1

[0039] The MOFs functionalized adsorption tube is used to selectively capture the volatile gas generated in the petrochemical industry; the inside of the MOFs functionalized adsorption tube is sequentially filled with a silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a mixed layer of a poly2, 6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and a carbon molecular sieve adsorbent;

[0040] The captured volatile gas is desorbed from the adsorption tube through a two-stage thermal desorption process;

[0041] The desorbed volatile gas is introduced into a gas chromatography-ion mobility spectrometry instrument for volatile gas content determination.​

[0042] The present application firstly uses a multi-layer MOFs functionalized adsorption tube to efficiently and selectively enrich VOCs with different properties. Secondly, through a precisely controlled two-stage thermal desorption procedure, VOC components with different volatility and polarity are released by category, reducing the subsequent GC separation pressure and improving resolution. Thirdly, using gas chromatography (GC), combined with a combination of pre-column (PLOT) and main column (ionic liquid column), fine separation of complex mixtures is achieved. Finally, ion mobility spectrometry (IMS) is used to quickly and highly sensitively detect the separated components using X-ray ionization and high-field gradient mobility tubes.

[0043] In some embodiments, the particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 80-120 mg;

[0044] The particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 130-170 mg;

[0045] The mixing ratio of the poly 2,6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and the carbon molecular sieve adsorbent is 1:(0.8-1.2), and the total filling amount is 180-220 mg.

[0046] In some embodiments, the Ag content of the silver ion modified UIO-66 metal organic framework is 5-15 wt% of the mass of the UIO-66. + The loading amount is 5-15 wt% of the mass of the UIO-66.

[0047] It should be noted that the MOFs functionalized adsorption tube is the core of gas capture, and the three materials filled in layers are used to selectively adsorb different types of volatile gases (benzene series, olefins, sulfur compounds, etc.) in petrochemical industry, and the specific effects are as follows:

[0048] The first layer is a silver ion modified UIO-66 metal organic framework: UIO-66 is a highly stable MOFs material (formed by Zr 4+ coordination with terephthalic acid), which has a regular porous structure (pore size about 0.8 nm) and a large specific surface area, and is suitable for adsorbing small molecule gases. Silver ions can form π-complexes with carbon-carbon double bonds in olefins, producing strong selective adsorption of olefin compounds (such as ethylene, propylene), solving the separation problem of olefins and other alkanes. The particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, which can ensure the gas flowability while increasing the specific surface area, and the filling amount is 80-120 mg, which can match the conventional concentration range of olefins and avoid incomplete desorption caused by excessive adsorption. The Ag + loading amount is 5-15 wt%, and the loading amount is too low, which will result in insufficient selectivity, and too high will occupy the pores of the UIO-66, reducing the adsorption capacity.

[0049] The second layer is copper benzene tricarboxylate (Cu-BTC): Cu-BTC is another MOFs material (Cu 2+ coordinated with benzene tricarboxylic acid), has a rich pore structure (pore size of about 0.9 nm), and Cu 2+ can form a coordination bond with S atoms in sulfur-containing compounds (such as hydrogen sulfide, mercaptans), and has a strong adsorption effect on sulfur-containing compounds. The particle size of copper benzene tricarboxylate is 60-80 mesh, which can match the first layer material, ensure the stability of the gas flow rate, and avoid uneven adsorption caused by the difference in interlayer resistance. The filling amount is 130-170 mg, and the concentration of sulfur-containing compounds in petroleum and chemical gases is usually low (ppm level), so a higher filling amount is required to ensure the capture efficiency.

[0050] The third layer is a mixed layer of poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent and carbon molecular sieve: poly-2,6-diphenyl-p-phenylene ether (PPE) in the poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent is a highly hydrophobic polymer that has strong affinity for non-polar benzene series (such as benzene, toluene, xylene); Graphitized carbon black (GCB) introduces carboxyl / hydroxyl groups after modification with mixed acid, enhancing the adsorption of polar molecules, and the two form a "core-shell structure" (GCB as core, PPE as shell), taking into account the adsorption of polar and non-polar gases. Carbon molecular sieve (CMS) has a very narrow microporous structure (pore size of 0.3-0.5 nm), and has strong adsorption capacity for small molecule alkanes (such as methane, ethane) and permanent gases, complementing PPE / GCB. The mixing ratio of poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent and carbon molecular sieve is 1:(0.8-1.2), which can balance the adsorption efficiency of benzene series and small molecule alkanes, and avoid insufficient adsorption of certain gases. The total filling amount is 180-220 mg, which serves as the "bottom" layer of the adsorption tube, covering the components not completely adsorbed by the previous two layers, and improving the overall capture rate.

[0051] In some embodiments, the preparation method of the poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent comprises:

[0052] Graphitized carbon black is reacted with mixed acid at 80°C for 6h, and after washing and drying, modified GCB containing carboxyl / hydroxyl groups is obtained;

[0053] The modified GCB is dispersed in a toluene solution of 2,6-diphenylphenol monomer, and a Cu + / amine complex catalyst formed by adding cuprous chloride and N,N-dimethyl-n-butylamine is introduced, and then oxygen is introduced at 75°C for 8h to obtain a reaction solution;

[0054] After the reaction solution is precipitated by methanol and centrifuged, and then sequentially washed by methanol and acetone, the core-shell composite poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent is obtained.

[0055] In some embodiments, the mixed acid is used in an amount of 100 mL per 10 g of graphitized carbon black, and the mixed acid is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1.

[0056] The mass ratio of the cuprous chloride to the N,N-dimethyl-n-butylamine is 1:2.4.

[0057] The mass ratio of the modified GCB to the 2,6-diphenylphenol monomer is 1:2.5.

[0058] In the process of modifying the graphitized carbon black (GCB) by mixed acid, the concentrated nitric acid in the mixed acid system is a strong oxidant, which can introduce carboxyl groups (-COOH); the concentrated sulfuric acid provides a proton environment, promotes the nitration reaction of nitric acid, and at the same time introduces part of the hydroxyl groups (-OH). The volume ratio of 3:1 of the concentrated nitric acid and the concentrated sulfuric acid can balance the oxidation intensity, and excessive nitric acid will cause excessive oxidation (structure damage) of the GCB, and excessive sulfuric acid will cause insufficient oxidation, resulting in poor modification effect. At the same time, a temperature of 80℃ for 6h is required, and a temperature that is too low will result in incomplete reaction, and a temperature that is too high will cause the GCB skeleton to be easily corroded, and 6h can ensure that the carboxyl groups / hydroxyl groups are fully generated. Limiting the amount of mixed acid (10 g of GCB + 100 mL) can ensure that the GCB is completely dispersed in the acid, and avoid local high concentration leading to uneven modification.

[0059] In the process of preparing the core-shell structure by in-situ polymerization, the Cu + complex formed by the catalyst (cuprous chloride: dimethyl-n-butylamine = 1:2.4) and the amine is a high-efficiency catalyst for the oxidative polymerization of 2,6-diphenylphenol, and excessive amine can stabilize the valence state of Cu + (avoiding oxidation to Cu 2+ ). Limiting the mass ratio of the modified GCB to the monomer to 1:2.5, the GCB is the core, and the monomer (2,6-diphenylphenol) forms a PPE shell layer after polymerization, and this ratio can ensure that the shell layer has a moderate thickness, and a too thin shell layer will have insufficient adsorption capacity, and a too thick shell layer will block the pores of the GCB. Oxygen is the oxidant for the polymerization reaction, and 75℃ is the optimal temperature for the reaction, and 8h ensures that the monomer is completely polymerized.

[0060] In some embodiments, the MOFs functionalized adsorption tube is made of stainless steel, has an inner diameter of 6-8 mm, and a length of 8-12 cm.

[0061] The material is stainless steel, which is firm and durable, can withstand high-pressure sampling and high-temperature desorption, has good chemical inertness, reduces adsorption and catalytic decomposition. The inner diameter (6-8 mm) and length (8-12 cm) can provide sufficient adsorbent filling space to ensure adsorption capacity; at the same time, the gas flow path is optimized to reduce dead volume and pressure drop, ensuring sampling and desorption efficiency.

[0062] In some embodiments, in the two-stage thermal desorption procedure, the first stage desorption temperature is 70-90℃, the high-purity hydrogen carrier gas flow rate is 0.8-1.2 mL / min, and the duration is 1.5-2.5 min, which is used to desorb C2-C5 light hydrocarbons; the second stage desorption temperature is 240-260℃, the high-purity hydrogen carrier gas flow rate is 1.8-2.2 mL / min, and the duration is 4-6 min, which is used to desorb benzene series and sulfur-containing compounds.

[0063] The purpose of thermal desorption is to release the captured gas in the adsorption tube completely and send it to the detection system. The two-stage procedure is designed for components with different adsorption strengths to avoid peak overlap caused by one-time high-temperature desorption.

[0064] In the first stage (70-90℃, carrier gas flow rate 0.8-1.2 mL / min, 1.5-2.5 min), the target components for thermal desorption are C2-C5 light hydrocarbons (such as ethane, propane, butane), which have weak adsorption (mainly physically adsorbed by CMS and PPE / GCB), and can be desorbed at low temperature. The desorption temperature is limited to 70-90℃, which is higher than the boiling point of light hydrocarbons (such as propane boiling point -42℃, butane -0.5℃), but lower than the desorption temperature of olefins and benzene series (to avoid interference caused by early desorption). The carrier gas flow rate is limited to 0.8-1.2 mL / min, which can ensure that light hydrocarbons are completely carried out, while avoiding peak broadening caused by excessive flow rate. The duration is limited to 1.5-2.5 min, which can ensure complete desorption of all light hydrocarbons (experimental verification of C2-C5 desorption half-life of about 1 min, 2.5 min can cover more than 99%).

[0065] In the second stage (240-260℃, carrier gas flow rate 1.8-2.2 mL / min, 4-6 min), the target components for desorption are benzene series (medium adsorption), sulfur-containing compounds (strong adsorption with Cu 2+ coordination), and olefins (strong adsorption with Ag⁺ complexation). The desorption temperature is limited to 240-260℃, which can break the π-complexation of Ag + with olefins, Cu 2+The coordination bond with sulfur, while the PPE / GCB adsorbed benzene series is completely desorbed (the glass transition temperature of PPE is about 220°C, and the polymer chain movement is enhanced at high temperature, releasing the adsorbed molecules). The carrier gas flow rate is limited to 1.8-2.2 mL / min, which is higher than the first stage, and can quickly bring high-boiling components into the chromatographic system, reducing the residue in the desorption tube. The duration is limited to 4-6 min, and the desorption of strongly adsorbed components requires a longer time, and 6 min can ensure complete release (avoiding the influence of residue on the next detection).

[0066] In some embodiments, in the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part uses an ionic liquid capillary column as the main column, with a length of 25-35 m, an inner diameter of 0.2-0.3 mm, and a membrane thickness of 0.15-0.25 μm; and is equipped with an Al2O3 / KCl PLOT pre-column, with a length of 8-12 m and an inner diameter of 0.3-0.4 mm.

[0067] GC-IMS realizes the qualitative and quantitative analysis of complex gases by combining the pre-separation of gas chromatography and the high-sensitivity detection of ion mobility spectrometry.

[0068] The gas chromatography (GC) uses an ionic liquid capillary column (main column, 25-35 m, 0.2-0.3 mm inner diameter, 0.15-0.25 μm membrane thickness), and the ionic liquid stationary phase has amphoteric polarity, which has good separation ability for polar (such as sulfur-containing compounds) and non-polar (such as benzene series) molecules, solving the problem of difficult separation of isomers (such as o- / m- / p-xylene) by traditional stationary phases. The length is limited to 25-35 m, which can balance the separation degree and analysis time (excessive length leads to peak broadening, and insufficient separation is incomplete); the inner diameter is limited to 0.2-0.3 mm, which can reduce the carrier gas flow rate and improve the column efficiency; and the membrane thickness is limited to 0.15-0.25 μm, which is suitable for light component separation. An Al2O3 / KCl PLOT pre-column (8-12 m, 0.3-0.4 mm inner diameter) is used, and the PLOT column (porous layer open-tube column) has strong retention ability for C1-C5 alkanes / alkenes, which can separate light hydrocarbons from heavy components (benzene series, sulfur-containing compounds) first, avoid the interference of light hydrocarbons with the separation of the main column, and improve the overall resolution.

[0069] In some embodiments, in the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part uses a 10 keV X-ray source as the ionization source, the migration tube length is 8-12 cm, the front-stage electric field gradient is 180-220 V / cm, the rear-stage electric field gradient is 380-420 V / cm, the drift gas is high-purity nitrogen, and the flow rate is 280-320 mL / min.

[0070] Ion mobility spectrometry (IMS) uses a 10 keV X-ray source as an ionization source, which can soft-ionize gas molecules into ions (avoiding too many fragments caused by hard ionization), and is suitable for detecting volatile organic compounds (VOCs). Compared with traditional radioactive sources (such as 63 Ni), the X-ray source is safer and has stable ionization efficiency. The length of the migration tube is limited to 8-12 cm. A shorter migration tube can shorten the analysis time (shorter ion migration distance), while ensuring sufficient separation space (too long will increase ion diffusion and reduce resolution). The electric field gradient of the front section is limited to 180-220 V / cm, and the electric field gradient of the rear section is limited to 380-420 V / cm. The two-stage gradient electric field can accelerate ion migration and reduce peak overlap of different ions (light ions reach the detector faster in the high electric field of the rear section, and heavy ions are fully separated in the low electric field of the front section). The drift gas (high-purity nitrogen, 280-320 mL / min) is chemically inert and does not interfere with ion migration; stable flow rate ensures uniform ion movement in the migration tube and improves detection repeatability. At the same time, a flow rate of 280-320 mL / min can quickly remove the detected ions to avoid residual interference.

[0071] In some embodiments, the volatile gas includes benzene series, olefins, and sulfur-containing compounds.

[0072] The present application forms a complete detection system through the selective capture of layered adsorption materials (for olefins, sulfur-containing compounds, and benzene series), stepwise release by two-stage thermal desorption (to avoid component interference), and high-resolution separation and detection by GC-IMS (accurate qualitative and quantitative). Each parameter (such as material particle size, packing amount, temperature, flow rate, etc.) is designed around "improve selectivity, reduce detection limit, and shorten analysis time" to ultimately achieve efficient detection of complex volatile gases in petrochemical industry.

[0073] The volatile gas detection method based on gas chromatography-ion mobility spectrometry (GC-IMS) proposed in the present application has significant advantages in the detection of complex volatile gases (benzene series, olefins, sulfur-containing compounds, etc.) in the petrochemical industry, which can be summarized as the following six points:

[0074] (1) High selectivity capture: through the synergistic design of three layers of functionalized adsorption materials, precise capture of different types of target substances is achieved. The first layer of Ag + -UIO-66 utilizes Ag + π-complexation with olefins for specific adsorption of olefins, solving the separation pain point of olefins and alkanes; the second layer of Cu-BTC utilizes Cu 2+The coordination with the sulfur atom selectively adsorbs low-concentration sulfur compounds (ppm level) with strong selectivity; the third layer PPE / GCB mixed layer of the CMS layer can adsorb benzene series (non-polar) and small-molecule alkanes (polar / weakly polar), forming a "full-coverage" capture system. The layered design avoids the interference problem caused by the "indiscriminate adsorption" of traditional adsorption materials, greatly improving the detection specificity.

[0075] (2) High-efficiency thermal desorption: Two-stage gradient thermal desorption program precisely regulates different adsorption strengths of target substances. In the low-temperature stage (70-90°C), weakly adsorbed C2-C5 light hydrocarbons are desorbed specifically to avoid interference with heavy components; in the high-temperature stage (240-260°C), strongly adsorbed olefins, sulfur compounds, and benzene series are efficiently released to ensure complete desorption (residual rate <1%). Compared with single-temperature desorption, the graded release makes the peak type clearer in subsequent GC-IMS analysis, with a separation degree improved by more than 30%.

[0076] (3) Material performance optimization: Ag + The precise control of particle size (60-80 mesh) and Ag + loading (5-15wt%) of UIO-66 balances flowability and adsorption efficiency, and the olefin adsorption capacity can reach 2.5 times that of traditional activated carbon; the core-shell structure design of PPE / GCB composite adsorbent (GCB as core, PPE as shell) makes the benzene series adsorption efficiency improve by 40%, and the temperature resistance is excellent (can withstand thermal desorption above 300°C); the particle size of the three-layer material is uniform (60-80 mesh), ensuring stable gas flow rate (fluctuation <5%), avoiding uneven adsorption caused by resistance difference between layers.

[0077] (4) GC-IMS combination: High-resolution separation combined with high-sensitivity detection, the ion liquid main column (25-35m) of the gas chromatography part combined with the Al2O3 / KCl PLOT pre-column separates the benzene series isomers (such as o- / m- / p-xylene) with a separation degree of more than 1.5, and the separation time of light hydrocarbons and heavy components is shortened to within 10 minutes; the 10keV X-ray source of the ion mobility spectrometry part realizes soft ionization (fragmentation rate <5%), and the gradient electric field drift tube (8-12cm) makes the ion separation efficiency improve by 25%, with a detection limit as low as ppb level (such as the detection limit of benzene 0.5ppb, hydrogen sulfide 0.2ppb). The combination technology combines the separation ability of GC and the high sensitivity of IMS, meeting the detection needs of "trace + complex components" in petrochemical industry.

[0078] (5) Operation safety and stability: The mixed acid modification (3:1 nitric acid-sulfuric acid) and in-situ polymerization parameters (temperature, catalyst ratio) are strictly controlled to ensure the batch stability of the PPE / GCB composite adsorbent; the X-ray source is used to replace the radioactive source to avoid radiation risk; the flow rates of the high-purity nitrogen drift gas (280-320 mL / min) and the carrier gas (hydrogen) are stable, so that the relative standard deviation (RSD) of the detection results is less than 3%; the adsorption tube material is stainless steel tube (inner diameter 6-8 mm, length 8-12 cm) with strong corrosion resistance, which can be reused more than 50 times to reduce the detection cost.

[0079] (6) Application scenario adaptation: The method provided in the application is designed specifically for typical volatile gases (benzene series, olefins, sulfur compounds) in the petrochemical industry, and can be directly applied to monitoring of tail gas of refining devices (such as olefin escape of catalytic cracking devices), leakage detection of storage tank area (such as benzene series volatilization and hydrogen sulfide corrosion early warning), and process gas component analysis (such as olefin purity determination). Compared with the traditional detection method (such as gas chromatography-mass spectrometry), no complex pretreatment is required, and the analysis time is shortened to 20 minutes, which is more suitable for on-site rapid detection.

[0080] The application will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not to limit the scope of the application. The experimental methods in the following examples are not specified, which are usually determined according to the industry standard. If there is no corresponding industry standard, the general international standard, conventional conditions, or the conditions recommended by the manufacturer are used.

[0081] The reagents and materials used in the detection method of the examples and comparative examples of the application are shown in Table 1, and the instruments and equipment used are shown in Table 2.

[0082] Table 1 Reagents and materials

[0083]

[0084] Table 2 Instruments and equipment

[0085]

[0086] Example 1

[0087] The example provides a detection method of volatile gas based on gas chromatography-ion mobility spectrometry, which can include the following steps:

[0088] S11, using a gas sampling pump and a MOFs functionalized adsorption tube to selectively capture volatile gases generated in petrochemical industry, the collection flow is 120 mL / min x 20 min (sampling volume 2.4 L), the ambient temperature is 45 DEG C; from the gas inlet end, the MOFs functionalized adsorption tube is sequentially filled with silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate and mixed layer of poly 2, 6-diphenyl ether / graphitized carbon black composite adsorbent and carbon molecular sieve adsorbent, and each layer is separated by quartz wool, and stainless steel screens are added at both ends;

[0089] The sampling point of the volatile gas is a catalytic cracking device exhaust cylinder (temperature 80 DEG C), the target VOCs are ethylene, propylene, benzene and methyl mercaptan, and the predicted concentration is 200-500 ppm of ethylene and 5-20 ppm of benzene.

[0090] The particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 100 mg; the particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 150 mg; the mixing ratio of the poly 2, 6-diphenyl ether / graphitized carbon black composite adsorbent and the carbon molecular sieve adsorbent is 1:1, and the total filling amount is 200 mg.

[0091] The Ag content of the silver ion modified UIO-66 metal organic framework is 10wt%. + The loading amount is 10wt% of the mass of UIO-66.

[0092] The preparation method of the silver ion modified UIO-66 metal organic framework comprises the following steps: 1g of UIO-66 is immersed in an AgNO3 aqueous solution, ultrasonic treatment is performed for 30 min, and then vacuum drying is performed at 80 DEG C for 6h to obtain Ag + The loading amount is 10wt% of the mass of UIO-66.

[0093] The preparation method of the poly 2, 6-diphenyl ether / graphitized carbon black composite adsorbent comprises the following steps: graphite carbon black is reacted with mixed acid at 80 DEG C for 6h, and after washing and drying, modified GCB containing carboxyl / hydroxyl is obtained; the modified GCB is dispersed in a toluene solution of 2, 6-diphenyl phenol monomer, and a Cu + / amine complex catalyst is added, then oxygen is introduced and reacted at 75 DEG C for 8h to obtain a reaction solution; after the reaction solution is precipitated by methanol and centrifuged, the core-shell composite poly 2, 6-diphenyl ether / graphitized carbon black composite adsorbent is obtained by washing with methanol and acetone in sequence.

[0094] The mixed acid is 100 mL, the volume ratio of concentrated nitric acid and concentrated sulfuric acid is 3:1, the mass ratio of cuprous chloride to N, N-dimethyl-n-butylamine is 1:2.4, and the mass ratio of modified GCB to 2, 6-diphenyl phenol monomer is 1:2.5.

[0095] The MOFs functionalized adsorption tube is made of stainless steel, with an inner diameter of 7 mm and a length of 10 cm.

[0096] S21, the captured volatile gas is desorbed from the adsorption tube by a two-stage thermal desorption process;

[0097] In the two-stage thermal desorption process, the first stage desorption temperature is 80℃, the high-purity hydrogen carrier gas flow rate is 1.0 mL / min, and the duration is 2.0 min, which is used for desorbing C2-C5 light hydrocarbons; the second stage desorption temperature is 250℃, the high-purity hydrogen carrier gas flow rate is 2.0 mL / min, and the duration is 5 min, which is used for desorbing benzene series and sulfur compounds.

[0098] S31, the desorption gas is directly connected to the GC injection port (transfer line temperature 150℃), which is used to introduce the desorbed volatile gas into the gas chromatography-ion mobility spectrometry instrument for content determination of the volatile gas.

[0099] In the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part uses an ionic liquid capillary column as the main column, with a length of 30 m, an inner diameter of 0.25 mm, and a film thickness of 0.20 μm; at the same time, an Al2O3 / KCl PLOT pre-column with a length of 10 m and an inner diameter of 0.32 mm is equipped.

[0100] In the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part uses a 10 keV X-ray source as the ionization source, the migration tube length is 10 cm, the front-stage electric field gradient is 200 V / cm, the rear-stage electric field gradient is 400 V / cm, the drift gas is high-purity nitrogen, and the flow rate is 300 mL / min.

[0101] The quantitative analysis results of the volatile gas of Example 1 are shown in Table 3.

[0102] Table 3 Quantitative analysis of volatile gas of Example 1

[0103]

[0104] The two-dimensional GC-IMS spectrum data of the volatile gas of Example 1 are shown in Table 4.

[0105] Table 4 Two-dimensional GC-IMS spectrum data of volatile gas of Example 1

[0106]

[0107] It should be noted that propylene and propane are baseline separated in the GC 8.2min + IMS 6.8-7.5ms region in the chromatogram, and benzene presents a sharp peak (half-peak width 0.12min) on the ionic liquid column, and the IMS migration peak symmetry factor is >0.95.

[0108] Example 2

[0109] The embodiment provides a volatile gas detection method based on gas chromatography-ion mobility spectrometry, which can comprise the following steps:

[0110] S11, using a gas sampling pump and a MOFs functionalized adsorption tube to selectively capture the volatile gas generated in the petrochemical industry, the collection flow rate is 120mL / minx20min (sampling volume 2.4L), and the environmental temperature is 45℃; from the gas inlet end, the MOFs functionalized adsorption tube is sequentially filled with a silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a mixed layer of a poly2,6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and a carbon molecular sieve adsorbent, while each layer is separated by quartz wool, and stainless steel screens are added at both ends;

[0111] The sampling point of the volatile gas is a styrene storage tank breather valve (room temperature), the target VOCs are styrene, ethylbenzene and hydrogen sulfide, and the predicted concentration is 50-200ppm of styrene.

[0112] The particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 80mg; the particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 170mg; the mixing ratio of the poly2,6-diphenyl p-phenylene ether / graphitized carbon black composite adsorbent and the carbon molecular sieve adsorbent is 1:0.8, and the total filling amount is 180mg.

[0113] The Ag content of the silver ion modified UIO-66 metal organic framework is 5wt%. + The loading amount is 5wt% of the mass of the UIO-66.

[0114] The preparation method of the silver ion modified UIO-66 metal organic framework comprises the following steps: 1g of UIO-66 is immersed in an AgNO3 aqueous solution, ultrasonic treatment is performed for 30min, and then vacuum drying is performed at 80℃ for 6h, to obtain Ag + The adsorbent has a loading amount of 5wt%.

[0115] The preparation method of the poly-2,6-diphenyl-1,1-phenylene ether / graphitized carbon black composite adsorbent comprises: reacting the graphitized carbon black with mixed acid at 80 DEG C for 6h, and after washing and drying, a modified GCB containing carboxyl / hydroxyl is obtained; dispersing the modified GCB in a toluene solution of 2,6-diphenylphenol monomer, and adding a Cu + / amine complex catalyst, and then introducing oxygen at 75 DEG C for 8h to obtain a reaction solution; after the reaction solution is precipitated by methanol and centrifuged, and then washed with methanol and acetone in sequence, a core-shell composite poly-2,6-diphenyl-1,1-phenylene ether / graphitized carbon black composite adsorbent is obtained.

[0116] The amount of the mixed acid is 100mL of mixed acid per 10g of graphitized carbon black, and the mixed acid is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1; the mass ratio of the cuprous chloride to the N,N-dimethyl-n-butylamine is 1:2.4; and the mass ratio of the modified GCB to the 2,6-diphenylphenol monomer is 1:2.5.

[0117] The MOFs functionalized adsorption tube is made of stainless steel, has an inner diameter of 7mm, and a length of 10cm.

[0118] S21, through a two-stage thermal desorption process, the captured volatile gas is desorbed from the adsorption tube;

[0119] In the two-stage thermal desorption process, the first stage desorption temperature is 70 DEG C, the high-purity hydrogen carrier gas flow rate is 0.8mL / min, and the duration time is 2.5min, which is used for desorbing C2-C5 light hydrocarbons; the second stage desorption temperature is 240 DEG C, the high-purity hydrogen carrier gas flow rate is 1.8mL / min, and the duration time is 6min, which is used for desorbing benzene series and sulfur-containing compounds.

[0120] S31, the desorption gas is directly connected to the GC injection port (the transmission line temperature is 150 DEG C), which is used to introduce the desorbed volatile gas into the gas chromatography-ion mobility spectrometry instrument for content determination of the volatile gas.

[0121] In the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part adopts an ionic liquid capillary column as a main column, with a length of 30m, an inner diameter of 0.25mm, and a film thickness of 0.20μm; and is equipped with an Al2O3 / KCl PLOT pre-column, with a length of 10m and an inner diameter of 0.32mm.

[0122] In the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part adopts a 10keV X-ray source as an ionization source, with a migration tube length of 10cm, a front-stage electric field gradient of 200V / cm, a rear-stage electric field gradient of 400V / cm, and a drift gas of high-purity nitrogen with a flow rate of 300mL / min.

[0123] The quantitative analysis results of the volatile gases of Example 2 are shown in Table 5.

[0124] Table 5 Quantitative analysis of volatile gases of Example 2

[0125]

[0126] The detected styrene concentration exceeded the limit (GB 37824 limit 50 ppm), and the flange sealing failure was located.

[0127] Example 3

[0128] The present embodiment provides a volatile gas detection method based on gas chromatography-ion mobility spectrometry, which can include the following steps:

[0129] S11, using a gas sampling pump and a MOFs functionalized adsorption tube to selectively capture the volatile gases generated in the petrochemical industry, the collection flow rate is 120 mL / min x 20 min (sampling volume 2.4 L), and the environmental temperature is 45℃; from the gas inlet end, the MOFs functionalized adsorption tube is sequentially filled with silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, and a mixed layer of poly2,6-diphenyl ether / graphitized carbon black composite adsorbent and carbon molecular sieve adsorbent, while each layer is separated by quartz wool, and stainless steel screens are added at both ends;

[0130] The sampling point of the volatile gas is the desulfurization tower outlet pipeline (temperature 60℃, containing H2S 100-500ppm), the target VOCs are H2S, methyl mercaptan and thiophene, and the detection difficulty is the inhibition of high concentration H2S to the detection of other sulfides.

[0131] The particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 120mg; the particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 130mg; the mixing ratio of the poly2,6-diphenyl ether / graphitized carbon black composite adsorbent and the carbon molecular sieve adsorbent is 1:1.2, and the total filling amount is 220mg.

[0132] The Ag content of the silver ion modified UIO-66 metal organic framework is 15wt% of the mass of UIO-66. + The loading amount is 15wt% of the mass of UIO-66.

[0133] The preparation method of the silver ion modified UIO-66 metal organic framework includes: taking 1g UIO-66 and immersing it in an AgNO3 aqueous solution, ultrasonicating for 30min, and then vacuum drying at 80℃ for 6h to obtain Ag + The loading amount is 15wt% of the mass of UIO-66.

[0134] The preparation method of the poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent comprises: reacting graphitized carbon black with mixed acid at 80℃ for 6h, and after washing and drying, modified GCB containing carboxyl / hydroxyl groups is obtained; dispersing the modified GCB in a toluene solution of 2,6-diphenylphenol monomers, and adding a Cu + / amine complex catalyst, and then introducing oxygen at 75℃ for 8h to obtain a reaction solution; after the reaction solution is precipitated by methanol and centrifuged, and then washed with methanol and acetone in sequence, a core-shell composite poly-2,6-diphenyl-p-phenylene ether / graphitized carbon black composite adsorbent is obtained.

[0135] The amount of the mixed acid is 100mL of mixed acid per 10g of graphitized carbon black, and the mixed acid is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1; the mass ratio of the cuprous chloride to the N,N-dimethyl-n-butylamine is 1:2.4; and the mass ratio of the modified GCB to the 2,6-diphenylphenol monomers is 1:2.5.

[0136] The MOFs functionalized adsorption tube is made of stainless steel, has an inner diameter of 7mm, and a length of 10cm.

[0137] S21, through a two-stage thermal desorption process, the captured volatile gas is desorbed from the adsorption tube;

[0138] In the two-stage thermal desorption process, the first stage desorption temperature is 90℃, the high-purity hydrogen carrier gas flow rate is 1.2mL / min, and the duration time is 1.5min, which is used for desorbing C2-C5 light hydrocarbons; the second stage desorption temperature is 260℃, the high-purity hydrogen carrier gas flow rate is 2.2mL / min, and the duration time is 4min, which is used for desorbing benzene series and sulfur-containing compounds.

[0139] S31, the desorption gas is directly connected to the GC injection port (the transmission line temperature is 150℃), which is used to introduce the desorbed volatile gas into the gas chromatography-ion mobility spectrometry instrument for content determination of the volatile gas.

[0140] In the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part uses an ionic liquid capillary column as the main column, with a length of 30m, an inner diameter of 0.25mm, and a film thickness of 0.20μm; at the same time, an Al2O3 / KCl PLOT pre-column with a length of 10m and an inner diameter of 0.32mm is provided.

[0141] In the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part uses a 10 keV X-ray source as an ionization source, the migration tube length is 10 cm, the front-stage electric field gradient is 200 V / cm, the rear-stage electric field gradient is 400 V / cm, the drift gas is high-purity nitrogen, and the flow rate is 300 mL / min.

[0142] The quantitative analysis results of the volatile gases of Example 3 are shown in Table 6.

[0143] Table 6 Quantitative analysis of volatile gases of Example 3

[0144]

[0145] In this example, thiophene and toluene co-elute (GC retention time 11.3 min), distinguished by IMS migration time difference (thiophene: 9.2 ms, toluene: 10.5 ms).

[0146] As can be seen, in Examples 1-3, the repeatability RSD < 5% (n = 6), the standard addition recovery is 93-102%, and the sulfide LOD ≤ 0.05 ppm (better than the standard HJ 1262-2022).

[0147] Comparative Example 1

[0148] This comparative example is based on the disclosure of Example 1, and the following modifications are made:

[0149] The MOFs functionalized adsorption tube does not contain silver ion modified UIO-66 metal organic framework.

[0150] The quantitative analysis results of the volatile gases of Comparative Example 1 are shown in Table 7.

[0151] Table 7 Quantitative analysis of volatile gases of Comparative Example 1

[0152]

[0153] No Ag in Comparative Example 1 + @UIO-66, missing olefin selective adsorption layer, ethylene / propylene detection amount drops by more than 70%, light hydrocarbons (C2-C5) are not effectively captured and directly penetrate the adsorption tube. The influence of benzene and methyl mercaptan is small (<10%), mainly borne by the middle and rear adsorption layers. Due to uneven distribution of light hydrocarbons in the adsorption tube, the desorption stability decreases and the RSD increases. Ag + The π complexation effect of Ag can concentrate trace amounts of olefins, and the absence of Ag reduces the signal-to-noise ratio and increases the LOD.

[0154] Comparative Example 2

[0155] This comparative example is based on the disclosure of Example 1, and the following modifications are made:

[0156] The MOFs functionalized adsorption tube does not contain copper benzene tricarboxylate.

[0157] The quantitative analysis results of the volatile gases of Comparative Example 2 are shown in Table 8.

[0158] Table 8 Quantitative analysis of volatile gases of Comparative Example 2

[0159]

[0160] There is no copper benzene tricarboxylate in Comparative Example 2, and the specific adsorption site of the sulfur-containing compound is missing, because Cu 2+ The strong coordination of the open site to the sulfur-containing substance disappears, and the detection amount of methyl mercaptan decreases. Although benzene can be adsorbed by the composite layer, the missing of the Cu-MOF in the middle section leads to the early desorption of part of the benzene, and the detection amount of benzene decreases. The sulfur compound is irreversibly adsorbed with the stainless steel tube wall during the desorption process, and the recovery rate plummets. Incomplete capture of sulfur compounds leads to fluctuation of GC-IMS response, and RSD significantly increases.

[0161] Comparative Example 3

[0162] This comparative example is based on the disclosure of Example 1, and the following modifications are made:

[0163] The MOFs functionalized adsorption tube does not contain a mixed layer of poly(2,6-diphenyl-p-phenylene oxide) / graphitized carbon black composite adsorbent and carbon molecular sieve adsorbent.

[0164] The quantitative analysis results of the volatile gases of Comparative Example 3 are shown in Table 9.

[0165] Table 9 Quantitative analysis of volatile gases of Comparative Example 3

[0166]

[0167] Comparative Example 3 has no composite adsorption layer, and the enrichment of benzene series and the humidity barrier are missing. The hydrophobic surface of poly(2,6-diphenyl-p-phenylene oxide) / GCB is the main adsorption site of aromatic hydrocarbons, and the detection amount of benzene decreases. Because of the absence of carbon molecular sieve, the humidity interference (RH=30%) is enhanced, and the RSD of methyl mercaptan increases. The composite layer provides a high specific surface area (>1000 m 2 / g) to concentrate trace VOCs, and the sensitivity decreases after the absence, and the LOD generally rises. The residual amount of benzene series increases during the high-temperature desorption stage, and the recovery rate is low.

[0168] Various embodiments of the application can exist in a variety of forms; it should be understood that the description of a specific form is merely an example and should not be construed as limiting the scope of the application; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it means to include any cited number (fraction or integer) within the indicated range.

[0169] In addition, in the description of the present application, the terms "include", "contain" and the like mean "include but not limited to". In this document, relational terms such as "first" and "second", and the like are used solely to distinguish one entity or action from another entity or action, and do not necessarily require or imply that these entities or actions are in any such actual relationship or order.

[0170] The above description is only a specific implementation of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A method for detecting a volatile gas based on gas chromatography-ion mobility spectrometry, characterized by, The method comprises: The MOFs functionalized adsorption tube is used for selectively capturing volatile gases generated in petrochemical industry; the inside of the MOFs functionalized adsorption tube is sequentially filled with a silver ion modified UIO-66 metal organic framework, copper benzene tricarboxylate, a mixed layer of a poly-2,6-diphenyl-1,4-phenylene oxide / graphitized carbon black composite adsorbent and a carbon molecular sieve adsorbent; The captured volatile gases are desorbed from the adsorption tube through a two-stage thermal desorption procedure; The desorbed volatile gases are introduced into a gas chromatography-ion mobility spectrometry instrument for content determination of the volatile gases; The preparation method of the poly-2,6-diphenyl-1,4-phenylene oxide / graphitized carbon black composite adsorbent comprises: The graphitized carbon black is reacted with mixed acid at 80℃ for 6h, and the modified GCB containing carboxyl / hydroxyl groups is obtained after washing and drying; The modified GCB was dispersed in a toluene solution of 2,6-diphenylphenol monomer and a Cu + / amine complex catalyst was added, and oxygen was then bubbled into the reaction solution at 75°C for 8 h to obtain a reaction solution. The reaction solution is precipitated and centrifuged with methanol, and then sequentially washed with methanol and acetone to obtain the core-shell poly-2,6-diphenyl-1,4-phenylene oxide / graphitized carbon black composite adsorbent.

2. The method according to claim 1, wherein, The particle size of the silver ion modified UIO-66 metal organic framework is 60-80 mesh, and the filling amount is 80-120mg; The particle size of the copper benzene tricarboxylate is 60-80 mesh, and the filling amount is 130-170mg; The mixing ratio of the poly-2,6-diphenyl-1,4-phenylene oxide / graphitized carbon black composite adsorbent to the carbon molecular sieve adsorbent is 1:(0.8-1.2), and the total filling amount is 180-220mg.

3. The method according to claim 2, wherein, Ag of the silver ion-modified UIO-66 metal organic framework + The loading is 5-15 wt% of the mass of UIO-66.

4. The method according to claim 1, wherein, The amount of mixed acid is 100mL per 10g of graphitized carbon black, and the mixed acid is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:1; The mass ratio of cuprous chloride to N,N-dimethyl-n-butylamine is 1:2.4; The mass ratio of the modified GCB to 2,6-diphenylphenol monomer is 1:2.

5.

5. The method according to claim 1, wherein, The MOFs functionalized adsorption tube is made of stainless steel, with an inner diameter of 6-8mm and a length of 8-12cm.

6. The method according to claim 1, wherein, In the two-stage thermal desorption procedure, the first-stage desorption temperature is 70-90℃, the flow rate of high-purity hydrogen carrier gas is 0.8-1.2mL / min, the duration is 1.5-2.5min, and it is used for desorbing C2-C5 light hydrocarbons; the second-stage desorption temperature is 240-260℃, the flow rate of high-purity hydrogen carrier gas is 1.8-2.2mL / min, the duration is 4-6min, and it is used for desorbing benzene series and sulfur-containing compounds.

7. The method according to claim 1, wherein, In the gas chromatography-ion mobility spectrometry instrument, the gas chromatography part uses an ionic liquid capillary column as the main column, with a length of 25-35m, an inner diameter of 0.2-0.3mm, and a film thickness of 0.15-0.25μm; an Al2O3 / KCl PLOT pre-column is also provided, with a length of 8-12m and an inner diameter of 0.3-0.4mm.

8. The method according to claim 1, wherein, In the gas chromatography-ion mobility spectrometry instrument, the ion mobility spectrometry part uses a 10keV X-ray source as the ionization source, with a migration tube length of 8-12cm, a front-stage electric field gradient of 180-220V / cm, a rear-stage electric field gradient of 380-420V / cm, and a drift gas of high-purity nitrogen with a flow rate of 280-320mL / min.

9. The method according to claim 1, wherein, The volatile gases include benzene series, olefins and sulfur compounds.

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