A system and method for determining the thermal stability of a chemical compound

Abstract

The present application provides a system and method for determining the thermal stability of chemical compounds, belonging to the field of chemical instruments and chemical process research methods. To solve the problems of low precision, poor automation and complex operation of pressure measurement under high temperature and high pressure conditions in the prior art. The Bourdon tube includes: a glass pressure diaphragm connected to a reaction container at one end and connected to a glass pointer indicator at the other end; a pressure compensation chamber in which the reaction container, glass pressure diaphragm and glass pointer indicator are placed; a gas distributor connected to the pressure compensation chamber, vacuum pump and gas cylinder respectively; a thermostat connected to the pressure compensation chamber for measuring the temperature of the pressure compensation chamber; the pressure compensation chamber is connected to an optical pointer position sensor, and the optical pointer position sensor is optically coupled with the glass pointer indicator. Used for studying homogeneous and heterogeneous reaction kinetics accompanied by gas phase molar mass change, and for thermodynamic analysis of substances in a wide temperature and pressure range.

Description

Technical Field

[0001] This invention belongs to the field of chemical instruments and chemical process research methods, and in particular relates to a system and method for determining the thermal stability of chemical compounds. Background Technology

[0002] In the fields of chemistry and chemical engineering, studying the kinetics of homogeneous and heterogeneous reactions accompanied by changes in the number of moles in the gas phase, as well as determining the thermodynamic properties of substances (such as thermal stability, boiling point, and critical parameters) over a wide range of temperature and pressure, has significant theoretical and applied value. Especially in areas such as fuel composition research, thermal decomposition mechanism analysis, and cold resource assessment, accurately determining the relationship between gas release and pressure changes during a reaction is crucial for obtaining kinetic parameters and thermophysical properties.

[0003] Currently, various devices and methods exist for measuring pressure changes in chemical reactions. Common technical solutions include directly measuring pressure changes within a closed reaction vessel using pressure sensors, or converting pressure changes into mechanical displacement through elastic elements (such as Boulden tubes or diaphragms). However, existing technologies have the following shortcomings in practical applications: Measurement accuracy and temperature / pressure range are limited: Traditional pressure sensors suffer from zero drift, decreased linearity, and poor long-term stability under high temperature (e.g., above 500°C) or wide pressure range (e.g., 0–30 atm) conditions, making it difficult to meet the requirements of high-precision measurement.

[0004] Inconvenient sealing of reaction vessel and inconvenient sample loading: In existing devices, the connection structure between the reaction vessel and the pressure measuring element is complicated, the sample loading and sealing operation is cumbersome, and it is difficult to achieve rigid fixation and convenient handling of the reaction vessel under high pressure compensation environment.

[0005] Insufficient pressure compensation and automatic control capabilities: Some devices use static pressure measurement methods, which cannot track the continuous pressure changes during the reaction process in real time. They lack automatic pressure compensation and closed-loop control functions, resulting in low data acquisition efficiency, excessive human intervention, and poor experimental reproducibility.

[0006] Inadequate temperature control and safety protection: Under high temperature and high pressure conditions, the existing equipment has insufficient temperature control accuracy and lacks multiple safety protection measures such as over-temperature and over-pressure protection, which poses certain operational risks. Summary of the Invention

[0007] In view of this, the present invention aims to provide a system and method for determining the thermal stability of chemical compounds, so as to solve the problems of low pressure measurement accuracy, poor automation and complex operation under high temperature and high pressure conditions in the prior art.

[0008] As one aspect of the present invention, to achieve the above-mentioned objective, the present invention adopts the following technical solution, providing a system for determining the thermal stability of chemical compounds, wherein the Boulden tube comprises: a glass pressure-measuring diaphragm and a reaction vessel, characterized in that: The pressure compensation chamber contains a reaction vessel, a glass pressure diaphragm, and a glass pointer indicator. The gas distributor is connected to the pressure compensation chamber, the vacuum pump, and the gas cylinder, respectively. A thermostat, connected to the pressure compensation chamber, is used to heat the pressure compensation chamber and maintain its temperature; The pressure compensation chamber is equipped with a fixed cup, and the reaction vessel is fixed to the center of the fixed cup by a clamping screw with a graphite liner. The bottom of the fixed cup is truncated conical. The pressure compensation cavity is connected to the optical pointer position sensor, and the optical pointer position sensor is optically coupled to the glass pointer indicator.

[0009] Furthermore, the reaction vessel is fixedly installed in a pressure compensation chamber.

[0010] Furthermore, the gas distributor is equipped with shut-off valves on the pipelines connecting it to the pressure compensation chamber, vacuum pump, and gas cylinder.

[0011] Furthermore, the thermostat includes two thermocouples, one of which is located inside the pressure compensation chamber and the other is located inside the thermostat.

[0012] Furthermore, a main electronic automatic pressure regulator and a backup manual regulator are arranged side by side between the gas cylinder and the gas distributor.

[0013] Furthermore, the main electronic automatic pressure regulator is controlled by the optical pointer position sensor to achieve opening and closing actions.

[0014] Furthermore, the gas distributor is also connected to a pressure sensor.

[0015] As another aspect of the present invention, a method for determining the thermal stability of a chemical compound includes the following steps: S1. The compound to be tested is loaded into the reaction vessel through the feed glass tube of the Boulden tube, and after the internal gas is extracted, the feed glass tube is melted off and then sealed. S2. The glass pointer indicator is fused at the weld point to fix the reaction vessel inside the pressure compensation chamber; S3. After the vacuum pump extracts the gas from the pressure compensation chamber, it is placed in a thermostat for heating. S4. When the optical pointer position sensor is triggered, the main electronic automatic pressure regulator opens and automatically supplies gas to the pressure compensation chamber through the gas distributor until the pointer returns to zero; at this time, the pressure sensor measures the pressure in the pressure compensation chamber. S5. The system enters pressure stabilization mode and waits for the next pointer deviation before repeating S4.

[0016] Furthermore, in S1, before loading the test compound into the reaction vessel, the sample is first frozen in liquid nitrogen to prevent the loss of volatile components.

[0017] Furthermore, in step S1, the reaction vessel is evacuated to a near-vacuum state.

[0018] Beneficial effects: 1. High measurement accuracy: It adopts a mechanical pressure sensing structure that combines a glass pressure diaphragm and a glass pointer indicator. Combined with the zero-point balancing method, it avoids the accuracy decay of electronic sensors under high temperature and high pressure environments, and the pressure measurement accuracy can reach ±0.1 bar.

[0019] 2. High degree of automation: Through closed-loop control of pointer position sensor and main electronic automatic pressure regulator, automatic pressure compensation and real-time tracking are achieved without manual intervention, which significantly improves experimental efficiency and data reliability.

[0020] 3. Wide range of applications: It can operate stably in the temperature range of 20-500°C and the pressure range of 0-30 atm, and is suitable for various application scenarios such as homogeneous and heterogeneous reaction kinetics research, thermal stability measurement and cold energy resource assessment. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system described in this invention; Figure 2 This is a flowchart of the method described in this invention; Figure 3 This is the kinetic curve of gas release during the butanol pyrolysis process in this embodiment of the invention; Figure 4 This is a circuit connection diagram of the present invention; Figure 5 This is a structural diagram of the fixed cup of the present invention; Figure 6 This is a structural diagram of a clamping screw with a graphite backing.

[0022] In the diagram: 1. Gas cylinder; 2. Vacuum pump; 3. Gas distributor; 4. Pressure compensation chamber; 5. Reaction vessel; 6. Glass pressure measuring diaphragm; 7. Glass pointer indicator; 8. Optical pointer position sensor; 9. Main electronic automatic pressure regulator; 10. Shut-off valve; 11. Pressure sensor; 12. Thermostat; 13. Fixed cup; 14. Clamping screw. Detailed Implementation Specific implementation method one: See appendix Figures 1 to 4This embodiment provides a system for measuring the thermal stability of chemical compounds. The Boulden tube includes a glass pressure diaphragm 6 and a reaction vessel 5. The pressure compensation chamber 4 contains the reaction vessel 5, the glass pressure measuring diaphragm 6, and the glass pointer indicator 7. Gas distributor 3 is connected to pressure compensation chamber 4, vacuum pump 2 and gas cylinder 1 respectively; Thermostat 12 is connected to the pressure compensation chamber 4 and is used to heat the pressure compensation chamber 4 and maintain its temperature. The pressure compensation chamber 4 is equipped with a fixed cup 13. The reaction vessel 5 is fixed to the center of the fixed cup by a clamping screw 14 with a graphite pad. The bottom of the fixed cup is truncated conical. The pressure compensation cavity 4 is connected to the optical pointer position sensor 8, and the optical pointer position sensor 8 is optically coupled to the glass pointer indicator 7.

[0024] In this embodiment, the reaction vessel 5 is fixedly installed in the pressure compensation chamber 4.

[0025] In this embodiment, the gas distributor 3 is equipped with a shut-off valve 10 on the pipelines connecting it to the pressure compensation chamber 4, the vacuum pump 2, and the gas cylinder 1.

[0026] In this embodiment, the thermostat 12 includes two thermocouples, one of which is located inside the pressure compensation chamber 4, and the other is disposed inside the thermostat 12. The temperatures inside the pressure compensation chamber 4 and the thermostat 12 are measured respectively.

[0027] In this embodiment, a main electronic automatic pressure regulator 9 and a backup manual regulator are arranged side by side between the gas cylinder 1 and the gas distributor 3.

[0028] During normal operation: In automatic mode, the main electronic automatic pressure regulator 9 automatically maintains the pointer at zero position; When higher sensitivity is required: the operator can switch to manual mode, turn off the electronic regulator, and use the manual regulator to finely adjust the pointer zero position, thereby improving the detection sensitivity to minute pressure changes.

[0029] In this embodiment, the main electronic automatic pressure regulator 9 is controlled by the optical pointer position sensor 8 to achieve opening and closing actions. When the optical pointer position sensor 8 is triggered, it automatically supplies gas to the pressure compensation chamber 4 until the pointer returns to zero. At this time, the pressure in the reaction vessel can be uniquely determined based on the pressure value in the compensation chamber.

[0030] In this embodiment, the gas distributor 3 is also connected to a pressure sensor 11.

[0031] Working principle: The optical pointer position sensor 8 uses a non-contact optical detection method and is optically coupled to the glass pointer indicator 7 to monitor the pointer deflection in real time. When the pressure inside the reaction vessel 5 changes due to a chemical reaction or physical change, the glass pressure-sensing diaphragm 6 deforms, causing the glass pointer indicator 7 to deviate from zero. After detecting the pointer deviation, the optical pointer position sensor 8 converts the optical signal into an electrical signal and transmits it to the signal converter.

[0032] The signal converter amplifies, filters, and performs analog-to-digital conversion on the electrical signal output from the sensor, converting it into a standard digital signal before transmitting it to the computer. The computer processes the signal according to a preset control algorithm, such as proportional-integral control, determines the direction and magnitude of the pointer deviation, and generates corresponding control commands.

[0033] The control command is output by the computer to the main electronic automatic pressure regulator 9. After receiving the command, the pressure regulator drives the connected shut-off valve 10 to open, so that the compressed air in the compressed air cylinder 2 enters the pressure compensation chamber 4 through the gas distributor 3, increasing the pressure in the chamber and pushing the glass pressure measuring diaphragm 6 to reset until the glass pointer indicator 7 returns to zero.

[0034] When the pointer returns to zero, the output signal of the optical pointer position sensor 8 changes accordingly. After the computer detects the zero signal, it issues a stop command. The main electronic automatic pressure regulator 9 closes the shut-off valve 10, the gas supply stops, and the system enters the pressure stabilization mode, waiting for the next pointer deviation.

[0035] Throughout the process, pressure sensor 11 measures the pressure at gas distributor 3 in real time and transmits the pressure data to a computer for recording and display. Since the pressure inside reaction vessel 5 is equal to the pressure inside pressure compensation chamber 4 when the pointer returns to zero, and the pressure inside pressure compensation chamber 4 is consistent with the pressure at gas distributor 3, the pressure value measured by pressure sensor 11 can accurately reflect the real-time pressure inside reaction vessel 5.

[0036] The computer automatically records and processes the relationship between the pressure of gaseous compounds in the reaction vessel and time, as well as the relationship between the chemical reaction rate constant and temperature, which is accompanied by the release of gaseous substances.

[0037] The pressure compensation chamber 4 is made of metal.

[0038] To ensure safety, the following protective measures are taken: valves for emergency pressure relief to the atmosphere, a system for quickly opening the thermostat door in case of overheating, short-circuit protection, and complete grounding of all electrical components of the device.

[0039] This structure enables high-precision measurement of gas release kinetics and thermophysical properties with high reproducibility over a wide range of temperatures and pressures.

[0040] The fixed cup 13 has threaded holes evenly distributed radially, preferably three around the circumference and six around the circumference. Each threaded hole is equipped with a clamping screw 14 with a graphite pad. The graphite pad contacts the reaction vessel 5 and the reaction vessel 5 is fixed by tightening the clamping screw 14. The contact end between the fixed cup 13 and the pressure compensation chamber 4 is a truncated cone shape, which facilitates positioning at the exact center of the pressure compensation chamber 4.

[0041] The lower part of the clamping screw 14 has a recess, and a graphite liner is embedded inside the recess, so that the graphite precipitate is in direct contact with the reaction vessel 5. Specific Implementation Method Two: A method for determining the thermal stability of a chemical compound includes the following steps: S1. The compound to be tested is loaded into the reaction vessel 5 through the feed glass tube of the Boulden tube. After the internal gas is extracted, the feed glass tube is melted and sealed. The compound to be tested is loaded into the reaction vessel 5 in liquid or solid form through the feed tube. After loading, the air in the reaction vessel 5 is extracted using the vacuum pump 2 until the residual pressure is close to zero. Then, the feed tube of the glass reaction vessel is sealed at the bottom of the glass pressure measuring diaphragm 6 using a gas torch.

[0043] S2. The glass pointer indicator 7 is fused at the weld point to fix the reaction vessel 5 inside the pressure compensation chamber 4; S3. After vacuum pump 2 extracts the gas from pressure compensation chamber 4, it is placed in thermostat 12 for heating. S4. When the optical pointer position sensor 8 is triggered, the main electronic automatic pressure regulator 9 opens and supplies gas to the pressure compensation chamber 4 through the gas distributor 3 until the pointer returns to zero; at this time, the pressure sensor 11 measures the pressure inside the pressure compensation chamber 4. S5. The system enters pressure stabilization mode and waits for the next pointer deviation before repeating S4.

[0044] In this embodiment, in step S1, before loading the test compound into the reaction vessel 5, the sample is first frozen in liquid nitrogen to prevent the loss of volatile components.

[0045] In this embodiment, during step S1, the reaction vessel 5 is evacuated to a near-vacuum state.

[0046] Example In studying the kinetic model of the pyrolysis process, the relationship between the amount of compound gas released and time was determined based on the pressure in the reaction vessel at different temperatures. Based on the obtained data, kinetic laws were established, and the chemical reaction rate constant was calculated. Figure 3 As shown.

[0047] The thermal decomposition of n-hydrocarbons proceeds according to a chain reaction mechanism and can be effectively described by first-order reaction equations. Taking butanol as an example, the main stages of pyrolysis were studied, including initiation, chain growth accompanied by the formation of intermediate free radicals, their decomposition, and the isomerization of terminal free radicals into intermediate free radicals.

[0048]

[0049] n is the number of moles of gaseous products ( ) ; The number of moles of gaseous products obtained by extrapolation to an infinite reaction time ( ) ; k is the reaction rate constant ( ) ; e is the base of the natural logarithm; Therefore, the rate constant of butanol has the following values:

[0050] This method can be used to determine the thermal stability of components, the rate of fuel pyrolysis reaction, and to assess the potential cold energy resources of fuel, as well as the boiling point and critical temperature in the range of 0 to 30 atm pressure and 20 to 500 °C temperature.

[0051] Computers, signal converters, and related control algorithms are all existing technologies and will not be described in detail here.

[0052] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A system for determining the thermal stability of a chemical compound, comprising a Boulden tube: The glass pressure-measuring diaphragm (6) and the reaction vessel (5) are characterized in that: The pressure compensation chamber (4) contains a reaction vessel (5), a glass pressure measuring diaphragm (6), and a glass pointer indicator (7). The gas distributor (3) is connected to the pressure compensation chamber (4), the vacuum pump (2) and the gas cylinder (1) respectively; The thermostat (12) is connected to the pressure compensation chamber (4) and is used to heat the pressure compensation chamber (4) and maintain its temperature; The pressure compensation chamber (4) is equipped with a fixed cup (13), and the reaction vessel (5) is fixed in the center of the fixed cup by a clamping screw (14) with a graphite pad. The bottom of the fixed cup is truncated conical. The pressure compensation chamber (4) is connected to the optical pointer position sensor (8), and the optical pointer position sensor (8) is optically coupled to the glass pointer indicator (7).

2. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: The reaction vessel (5) is fixedly installed in the pressure compensation chamber (4).

3. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: The gas distributor (3) is connected to the pressure compensation chamber (4), vacuum pump (2) and gas cylinder (1) through pipelines equipped with shut-off valves (10).

4. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: The thermostat (12) includes two thermocouples, one of which is located inside the pressure compensation chamber (4) and the other is located inside the thermostat (12).

5. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: A main electronic automatic pressure regulator (9) and a backup manual regulator are arranged side by side between the gas cylinder (1) and the gas distributor (3).

6. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: The main electronic automatic pressure regulator (9) is controlled by the optical pointer position sensor (8) to realize the opening and closing action.

7. The system for determining the thermal stability of a chemical compound according to claim 1, characterized in that: The gas distributor (3) is also connected to a pressure sensor (11).

8. A method for determining the thermal stability of a chemical compound, characterized in that, Using the system according to any one of claims 1 to 7, the steps include: S1. The compound to be tested is loaded into the reaction vessel (5) through the feed glass tube of the Boulden tube, and after the internal gas is extracted, the feed glass tube is melted and sealed. S2. The glass pointer indicator (7) is fused at the weld point to fix the reaction vessel (5) inside the pressure compensation chamber (4); S3. After the vacuum pump (2) extracts the gas from the pressure compensation chamber (4), it is placed in the thermostat (12) for heating. S4. When the optical pointer position sensor (8) is triggered, the main electronic automatic pressure regulator (9) is opened and gas is automatically supplied to the pressure compensation chamber (4) through the gas distributor (3) until the pointer returns to zero; at this time, the pressure sensor (11) measures the pressure in the pressure compensation chamber (4); S5. The system enters pressure stabilization mode and waits for the next pointer deviation before repeating S4.

9. The method for determining the thermal stability of a chemical compound according to claim 8, characterized in that: In step S1, before loading the test compound into the reaction vessel (5), the sample is first frozen in liquid nitrogen to prevent loss of volatile components.

10. The method for determining the thermal stability of a chemical compound according to claim 8, characterized in that: In step S1, the reaction vessel (5) is evacuated to a near-vacuum state.

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