Method for identifying and analyzing species in low-temperature oxidation process of isoprene

Abstract

According to the species identification and analysis method in the isoprene low-temperature oxidation process, the flow and temperature of reaction gas are accurately controlled through a feeding system, and different low-temperature oxidation conditions are simulated. Reaction gases are uniformly mixed through the jet stirring reactor, so that sufficient contact of reactants is ensured, and the reaction efficiency and uniformity are further improved. The method comprises the following steps: sampling at an outlet of a reactor by using a sampling tube, introducing mixed gas into a chromatographic column by adopting a non-split sample introduction mode beneficial to trace analysis, and realizing high-sensitivity species identification and measurement of a gas chromatography-time-of-flight mass spectrometer (GC-TOFMS); according to the method, through integrated system design, automation and high efficiency of an experiment process are realized, manual operation errors are reduced, and experiment precision and repeatability are improved. Meanwhile, the reaction process can be efficiently monitored, and accurate data support is provided for optimization of the low-temperature oxidation process.

Description

Technical Field

[0001] The present invention relates to the field of low-temperature oxidation of isoprene, and particularly to a method for identifying and analyzing species in the process of low-temperature oxidation of isoprene. Background Art

[0002] Alkenes are key intermediate products in the oxidation models of normal and branched alkanes. Like other species in detailed reaction kinetic mechanisms, it is necessary to use sub-mechanisms to describe the reactivity of these alkenes. The core task of the alkene sub-mechanism is to provide an approximate path to promote the conversion of atoms generated in alkenes into smaller products and then further into final products. Since the concentration of alkene intermediates is usually at a relatively low level, most alkene sub-mechanisms are relatively crude. In addition, there is less data available for improving the alkene reaction mechanism, which also limits the development of the alkene sub-mechanism. With the continuous in-depth study of fuel combustion reaction kinetics, the reaction mechanism of alkenes has received increasing attention, and it is expected that they can provide more accurate model results for alkanes.

[0003] The autoignition process of fuel includes three stages: low-temperature oxidation, self-heating, and combustion. Among them, the initial heat accumulated in the low-temperature oxidation stage is the key to fuel autoignition. Moreover, the ignition time, power output, fuel flexibility, fuel economy, and emissions under autoignition conditions are also affected by the low-temperature oxidation reaction. In the process of low-temperature oxidation, small molecule free radicals will first attack the fuel, thereby generating fuel free radicals. The fuel free radicals then initiate chain propagation and chain branching reactions. Among them, peroxyalkyl free radicals (ROO·) and their subsequent related reactions play an important role in this process.

[0004] Therefore, in order to improve the economy and environmental protection of fuel combustion, promote the application research and development of new fuels, and rationally utilize the autoignition phenomenon for the design and optimization of engines, it is necessary to understand and analyze the low-temperature oxidation reaction kinetics more deeply. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention proposes a method for identifying and analyzing species in the process of low-temperature oxidation of isoprene. This method can precisely control the reaction conditions, capture samples and analyze the species composition with high sensitivity, reduce the manual operation error, improve the experimental accuracy and reliability, and provide reliable experimental data and theoretical basis for the optimization of the low-temperature oxidation process.

[0006] The technical solution of the present invention is realized as follows:

[0007] A method for identifying and analyzing species in the process of low-temperature oxidation of isoprene, characterized by comprising the following steps:

[0008] Step 1: Use a liquid flow controller to inject fuel into the vaporization device to convert the liquid fuel into a gas;

[0009] Step 2: The mixed fuel, oxygen, and dilution gas enter the jet stirred reactor after preheating and undergo a low-temperature oxidation reaction

[0010] Step 3: Use a sampling tube to take samples at the reactor outlet, and adopt a splitless injection mode that is conducive to trace analysis to introduce the mixed gas into the chromatographic column;

[0011] Step 4: Use gas chromatography (GC) to separate the fuel and oxidation products, and use time-of-flight mass spectrometry (TOFMS) to identify each component and obtain their signal intensity distributions;

[0012] Step 5: Through a computer data acquisition and processing system, process and analyze the GC-TOFMS data to obtain the mass spectra and signal intensity diagrams of each product during the low-temperature oxidation of isoprene.

[0013] A further improvement lies in that: in the said Step 1, the purpose of using the liquid flow controller is to achieve precise metering and control of the liquid fuel, and the function of the vaporization device is to convert the liquid fuel into a gas to facilitate full mixing with the oxidant in the subsequent oxidation reaction.

[0014] A further improvement lies in that: in the said Step 2, the purpose of setting a short annular preheating zone is to heat the inlet mixture in a very short time to achieve more reliable temperature uniformity in the reactor. Jet stirring can effectively avoid uneven gas distribution or insufficient contact of reactants, thereby improving the reaction rate and the uniformity of the reaction.

[0015] A further improvement lies in that: in the said Step 3, use a sampling tube to take samples at the reactor outlet, use a peristaltic pump to enable the reaction products to enter the chromatographic injection port, adopt a splitless injection mode, and after most of the samples are introduced into the chromatographic column, open the split valve to discharge the remaining vapor in the liner. This mode is conducive to trace analysis.

[0016] A further improvement lies in that: in the said Step 4, the separation of the sample is achieved through the adsorption and elution characteristics of different components in the gas chromatography analysis column. In mass spectrometry, various compounds are accurately identified and analyzed by ionizing the sample and measuring the flight time of the ions.

[0017] A further improvement lies in that: in the said Step 5, automatically collect and process various data during the experiment to help researchers quickly understand the experimental results and provide data support for further reaction optimization.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] By precisely adjusting the flow rate and temperature of the gas through the feeding system, different low-temperature oxidation reaction conditions can be accurately simulated. The jet stirring reactor can better ensure the uniform distribution of the gas, improve the reaction efficiency and reduce the error caused by uneven gas flow. The gas chromatography and time-of-flight mass spectrometry (GC-TOFMS) are used to detect the collected samples, providing extremely high sensitivity and resolution, and providing detailed species composition data for the study of the reaction mechanism in the low-temperature oxidation process. This method is not only applicable to the low-temperature oxidation process of isoprene, but also can be extended to the species analysis of other complex chemical reaction systems, with strong generality and operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. The drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0021] Figure 1 Schematic diagram of the steps of the present invention;

[0022] Figure 2 Mass spectrometry diagram of some species of the present invention;

[0023] Figure 3 Signal intensity diagram of some species of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] See Figure 1 , the present invention discloses a method for species identification and analysis in the low-temperature oxidation process of isoprene, including the following steps:

[0027] Step 1: Use a liquid flow controller to inject fuel into the vaporization device to convert the liquid fuel into a gas.

[0028] Step 2: The mixed fuel, oxygen, and dilution gas enter the jet-stirred reactor after preheating and undergo a low-temperature oxidation reaction. The experimental conditions are shown in Table 1.

[0029] Table 1 Experimental conditions for the low-temperature oxidation of isoprene

[0030]

[0031] Step 3: Use a sampling tube to take samples at the reactor outlet and introduce the mixed gas into the chromatographic column using a splitless injection mode that is conducive to trace analysis.

[0032] Step 4: Use gas chromatography (GC) to separate the fuel and oxidation products, and use time-of-flight mass spectrometry (TOFMS) to identify each component and obtain their signal intensity distributions.

[0033] Step 5: Through a computer data acquisition and processing system, process and analyze the GC-TOFMS data to obtain the mass spectra and signal intensity diagrams of each product during the low-temperature oxidation of isoprene, as shown in Figure 2 and Figure 3 respectively. Due to the metal ionization effect, species (H2O, CO, CO2) with ionization energies higher than the ion source (10.6 eV) will also be ionized; the mass-to-charge ratios (m / z) of CO2 and C2H4O are similar, and the judgment is made by magnifying the mass spectrum.

[0034] In the above Step 1, the purpose of using a liquid flow controller is to achieve precise metering and control of the liquid fuel. The role of the vaporization device is to convert the liquid fuel into a gas, so as to facilitate full mixing with the oxidant in the subsequent oxidation reaction. Through this precise control and conversion, the system can ensure that the reaction proceeds under ideal conditions, improving the controllability and consistency of the reaction. In addition, this design reduces the risk of incomplete combustion and harmful emissions, helps reduce environmental pollution, and improves the safety and reliability of the system.

[0035] In the above Step 2, the purpose of setting a short annular preheating zone is to heat the inlet mixture in a very short time to achieve more reliable temperature uniformity in the reactor. Jet stirring can effectively avoid uneven gas distribution or insufficient contact between reactants, thereby increasing the reaction rate and the uniformity of the reaction. In addition, uniform gas mixing can reduce the risk of local overheating and incomplete reactions, further optimizing the reaction process and improving the quality and stability of the products.

[0036] In the third step, a sampling tube is used to take samples at the reactor outlet. A peristaltic pump is used to make the reaction products enter the chromatograph injection port. The splitless injection mode is adopted. After most of the samples are introduced into the chromatographic column, the split valve is opened to discharge the remaining vapor in the liner. This mode is beneficial for trace analysis.

[0037] In the fourth step, by analyzing the adsorption and elution characteristics of different components in the gas chromatograph column, the components in the sample are separated. The high-efficiency separation function of the gas chromatograph ensures the purity of each component in the complex sample and avoids interference between components. In the mass spectrometer, by ionizing the sample and measuring the flight time of ions, the molecular structures and masses of various compounds are accurately identified. At the same time, the mass spectrometer can analyze the signal intensities of each component in the sample and provide detection results with high sensitivity and high resolution.

[0038] In the fifth step, by collecting and processing various data during the experiment, researchers can efficiently and accurately master the reaction process and the changes in its key parameters. This not only saves manual operation time but also eliminates human errors, ensuring the accuracy and consistency of the data. At the same time, by continuously tracking and analyzing the experimental data, researchers can quickly identify potential problems in the reaction and adjust and optimize the reaction conditions according to the feedback.

[0039] A liquid flow controller is used to inject fuel into the vaporization device. After the fuel is vaporized, it is mixed with oxygen and dilution gas and enters the jet stirred reactor through a pipeline. A K-type thermocouple is installed at the center of the jet stirred reactor to monitor the reaction temperature. A ring-shaped preheating zone is fixedly arranged at the top of the reactor to heat the inlet mixture in a very short time and achieve more reliable temperature uniformity in the reactor. A sampling tube is used to take samples at the reactor outlet. The splitless injection mode, which is beneficial for trace analysis, is adopted to introduce the mixed gas into the chromatographic column. The separation of the sample is achieved through the adsorption and elution characteristics of different components in the gas chromatograph column. In the mass spectrometer, by ionizing the sample and measuring the flight time of ions, various compounds are accurately identified and analyzed. Finally, the experimental results are displayed on the data acquisition and processor.

[0040] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for species identification and analysis in the low-temperature oxidation process of isoprene, characterized in that, It includes the following steps: Step 1: Use a liquid flow controller to inject fuel into a vaporization device to convert the liquid fuel into a gas; Step 2: The mixed fuel, oxygen, and dilution gas enter a jet stirred reactor after preheating and undergo a low-temperature oxidation reaction; Step 3: Use a sampling tube to take a sample at the reactor outlet, and introduce the mixed gas into the chromatographic column in a splitless injection mode that is conducive to trace analysis; Step 4: Use gas chromatography (GC) to separate the fuel and oxidation products, and use time-of-flight mass spectrometry (TOFMS) to identify each component and obtain their signal intensity distributions; Step 5: Through a computer data acquisition and processing system, process and analyze the GC-TOFMS data to obtain the mass spectra and signal intensity maps of each product during the low-temperature oxidation of isoprene.

2. The method for species identification and analysis in the low-temperature oxidation process of isoprene according to claim 1, wherein: In Step 1, the purpose of using a liquid flow controller is to achieve precise metering and control of the liquid fuel, and the role of the vaporization device is to convert the liquid fuel into a gas to facilitate sufficient mixing with the oxidant in the subsequent oxidation reaction.

3. The method for species identification and analysis in the low-temperature oxidation process of isoprene according to claim 1, characterized in that: In Step 2, the purpose of setting a short annular preheating zone is to heat the inlet mixture in a very short time to achieve more reliable temperature uniformity in the reactor.

4. The method for species identification and analysis in the low-temperature oxidation process of isoprene according to claim 1, characterized in that: In Step 3, use a sampling tube to take a sample at the reactor outlet, use a peristaltic pump to enable the reaction products to enter the chromatographic injection port, and in the splitless injection mode, after most of the sample is introduced into the chromatographic column, open the split valve to discharge the remaining vapor in the liner. This mode is conducive to trace analysis.

5. A method for identifying and analyzing species in the low-temperature oxidation process of isoprene according to claim 1, characterized in that: In Step 4, the separation of the sample is achieved through the adsorption and elution characteristics of different components in the column, and various compounds are accurately identified and analyzed by ionizing the sample and measuring the flight time of the ions.

6. The medium and low temperature oxidation experimental method in an isoprene jet stirring reactor according to claim 1, characterized in that: In Step 5, automatically collect and process various data during the experiment to help researchers quickly understand the experimental results and provide data support for further reaction optimization.

Images