A device and method for testing the decomposition kinetics of hydrogen iodide.

Abstract

This invention belongs to the field of renewable energy power testing technology, and discloses a device and method for testing the decomposition kinetics of hydrogen iodide. A certain mass of catalyst sample is weighed using an electronic balance and filled into the middle of a reaction tube, which is then fixed with high-purity silica wool on both sides. A bidirectional injection pump is used to introduce HI solution into an HI evaporator; the vaporized HI gas is then purged with N2 and enters the reaction tube. After catalytic reaction in a fixed-bed reactor, the reaction mixture is first condensed in a condenser and then separated in a gas-liquid separator. Acidic gas impurities and water are removed using NaOH solution and silica gel. Finally, only a mixture of N2 and H2 is allowed to enter a hydrogen analyzer, where a thermal conductivity hydrogen analyzer is used to measure the H2 concentration at the outlet. This invention determines the corresponding kinetic parameters and simultaneously applies the catalyst to the reactor design process, analyzing the impact of different types of catalysts on reactor performance.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy kinetic testing technology, and particularly relates to a hydrogen iodide decomposition kinetic testing device and method. Background Technology

[0002] Currently, with the rapid development of society and economy, people's demand for energy continues to increase. Traditional fossil fuels, due to their limited storage and environmental unfriendliness, are unable to meet the energy needs of today's society. Therefore, it is urgent to find a new energy source to replace traditional fossil fuels. Hydrogen energy is a clean and renewable energy source, and vigorously developing hydrogen energy is crucial for addressing issues such as the energy crisis and the greenhouse effect. Based on the carbon emissions of hydrogen production pathways, hydrogen production methods can be divided into three types: gray hydrogen, blue hydrogen, and green hydrogen. The sulfur-iodine (SI) thermochemical cycle is a green hydrogen production method and has been proven to be one of the best thermochemical cycle methods through a series of evaluation studies. The SI cycle uses water (H2O) as raw material and decomposes H2O into hydrogen (H2) and oxygen (O2) through a series of chemical reactions. It has advantages such as zero carbon emissions, compatibility with high-temperature gas-cooled reactors, ease of large-scale production, and high energy efficiency. 4] The SI thermochemical cycle mainly consists of the following reaction processes:

[0003]

[0004] Reaction (1) is the Bunsen reaction, which is exothermic and produces a two-phase solution of hydrogen iodide (HI) and sulfuric acid (H2SO4). After a series of purification and separation processes, H2SO4 and HI gases are obtained. Reaction (2) and reaction (3) are the decomposition reactions of H2SO4 and HI, respectively. Both are endothermic reactions. The sulfur dioxide (SO2) and iodine (I2) generated by the decomposition reaction are recycled as intermediate products in the reaction system. After a series of cycles, H2O is finally decomposed into H2 and O2. As the only hydrogen generation step in the SI thermochemical cycle, the HI decomposition reaction directly affects the H2 yield and thermal efficiency of the system. Therefore, this decomposition process is one of the key factors affecting the thermal efficiency of the SI process. The HI decomposition reaction is limited by thermodynamic equilibrium conditions. The equilibrium conversion rate is low at low temperatures, and the reaction proceeds slowly without a catalyst. To improve the reaction rate, a suitable catalyst is usually needed in the HI decomposition process. Currently, the research on the HI decomposition reaction mainly focuses on catalyst performance testing, kinetic mechanism research, coupling with high-temperature helium, and novel membrane reactors. Singhania et al. provided a detailed review of the development of HI decomposition catalysts and pointed out that future research trends lie in further developing novel catalysts based on nanostructures and composite materials. Xu et al. prepared Ni-Ir bimetallic catalysts supported on activated carbon, while Zhang et al. studied Pt-Ir bimetallic catalysts and applied them to the HI decomposition reaction. Compared with monometallic catalysts, the bimetallic catalysts significantly improved catalytic activity and stability. Li et al. investigated the effect of different N doping on the activity of activated carbon catalysts, showing that N doping improved the catalytic effect and that the HI conversion rate was proportional to the N content. Shin et al. studied a semi-pilot-scale HI decomposition reactor coupled with a helium loop, simulating the effect of different shell-and-tube heat transfer coefficients on the helium outlet temperature and HI conversion rate. Kong et al. used finite-time thermodynamics to study a high-temperature helium-heated HI decomposition reactor, optimizing the reactor heat source temperature with the goal of minimizing entropy production. Myagmarjav et al. prepared a HI decomposition silicon membrane reactor and conducted theoretical and experimental studies on membrane reactors with different HI flow rates and purge flow rates, confirming the consistency of the results. Myagmarjav et al. further analyzed the influence of different membrane reactor operating conditions on HI conversion and discussed the modular design of membrane reactors. Bhushan et al. prepared a thin-layer tantalum membrane reactor and conducted HI decomposition experiments, achieving an HI conversion rate of 94.7% at 723 K. Nailwal et al. first prepared a multi-tube Ta membrane reactor and tested HI decomposition membrane reactors under different operating parameters, achieving a single-pass conversion rate of 70%-88%. Kong et al. also studied the influence of different purge gases on the performance of HI decomposition membrane reactors, showing that a higher HI conversion rate and H2 recovery rate were more easily obtained under countercurrent purge mode.The above studies have advanced the research on HI decomposition reaction from different aspects. Among them, catalyst performance testing and kinetic mechanism research are the foundation of various studies and can provide a basis for the design and optimization of HI decomposition reactors. Regarding catalyst kinetics, Oosawa et al. proposed a Langmuir-Hinshelwood rate equation for HI decomposition and tested the kinetics of the HI catalytic decomposition reaction using AC and 1.05 wt% AC-supported platinum (Pt / AC) catalysts under conditions of 1 atm pressure and 500-700 K. The results showed that water vapor has a relatively small impact on the HI decomposition reaction rate and equilibrium state; however, iodine has a significant inhibitory effect on the HI decomposition rate below 550 K. Shindo et al. derived a new HI decomposition rate equation and conducted a kinetic study on the HI decomposition reaction process using 0.5 wt% Pt / γ-Al₂O₃ as a catalyst. The results showed a good correlation between the experimental data and the equation. Favuzza et al. proposed a new decomposition mechanism and tested commercial AC particles as a catalyst for the HI decomposition reaction in a temperature range of 240-500 °C. In the experiment, HI azeotropic solution and pure HI gas were used for testing, and the corresponding kinetic parameters were obtained. Nguyen et al. prepared a Pt / Al2O3 catalyst and carried out HI decomposition reaction kinetic experiments at 350-550℃ and atmospheric pressure. Using the experimental data, new kinetic parameters were obtained. The study found that when a small amount of iodine is present in the feed, the HI conversion efficiency is significantly reduced.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0006] Existing commercial catalysts are widely used due to the maturity of their preparation processes and their economic efficiency. However, there are currently few kinetic studies on different commercial catalysts for the HI decomposition reaction, and there is a lack of comparative kinetic tests between different commercial catalysts.

[0007] Furthermore, HI solution is often used as the feed solution in HI decomposition kinetic experiments, and a small amount of I2 is inevitably present in the solution. There is a lack of universal and effective testing devices and methods for reaction kinetic experiments under these conditions. If the HI feed solution contains varying degrees of iodine due to oxidation, it will lead to deviations in the kinetic experimental tests, preventing researchers from accurately grasping the true catalytic characteristics of different commercial catalysts. The invention proposes an HI decomposition kinetic testing device and method, including experimental platform testing, equation derivation, and data processing. This provides methodological guidance for determining the kinetic parameters of commercial HI decomposition catalysts, which is beneficial for expanding the industrial application of commercial catalysts, effectively reducing reactor design costs, and improving the overall efficiency of hydrogen production systems. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides a device and method for testing the decomposition kinetics of hydrogen iodide.

[0009] This invention is implemented as follows: a method for testing the decomposition kinetics of hydrogen iodide, the method comprising the following steps:

[0010] The first step is to weigh a certain mass of catalyst sample using an electronic balance and fill it into the middle of the reaction tube, then fix it with high-purity quartz wool on the top and bottom sides.

[0011] The second step involves using a two-way injection pump to pass the HI solution into the HI evaporator, and the vaporized HI gas is then purged by N2 and enters the reaction tube together.

[0012] The third step involves catalytic reaction in a fixed-bed reactor, followed by condensation of the reaction mixture in a condenser, and then separation in a gas-liquid separator.

[0013] The fourth step involves removing acidic gaseous impurities and water using sodium hydroxide solution and silica gel. Finally, only a mixture of N2 and H2 is allowed to enter the hydrogen analyzer, and a thermal conductivity hydrogen analyzer is used to measure the H2 concentration at the outlet.

[0014] Furthermore, the liquid feed rate in the second step is set to 0.05-0.35 mL / min; the N2 flow rate is 50-350 mL / min.

[0015] Furthermore, the temperature, flow rate, pressure, and H2 concentration data of the hydrogen iodide decomposition kinetics test method are monitored and collected in real time using a data acquisition system at a data acquisition frequency of 1 second / time. After each change in the HI feed flow rate, the reaction process will reach an equilibrium state after a period of change. When the collected hydrogen concentration is observed to remain unchanged within 15 minutes, the reaction system reaches a stable state. The H2 concentration and outlet gas flow rate at this time are recorded and used for subsequent data processing.

[0016] Furthermore, the conversion rate of HI in the hydrogen iodide decomposition kinetics test method is determined by collecting the gas flow rate Q at the outlet. V The H2 concentration C measured by the hydrogen analyzer H2 The calculation yields the following formula:

[0017]

[0018] In the formula, Q F Q represents the feed rate of the HI solution, expressed in mL / min. V The total flow rate of N2 and H2 gases at the outlet, expressed in mL / min, w HI The density and mass fraction of the HI solution are M, respectively. HIThe value is the molar mass of HI, expressed in g / mol.

[0019] Furthermore, based on the measurement accuracy of the push-pull syringe pump, mass flow meter, and hydrogen analyzer, and according to the error propagation formula, the relative error of HI conversion rate is derived:

[0020]

[0021] The relative error of HI for a single measurement was found to be 3.5% based on the measurement data.

[0022] Furthermore, the commercially available catalysts used in the hydrogen iodide decomposition kinetics test method are activated carbon (AC) and alumina-supported platinum (Pt / Al2O3) catalysts. The activated carbon is processed by steam activation followed by acid washing, and the catalyst particles are cylindrical with a particle size of 0.8 mm. The Pt / γ-Al2O3 catalyst is processed by impregnation and calcination, with a Pt loading mass fraction of 0.5% and a particle size of 3.2 mm. The reagent used is hydroiodic acid solution, yielding a HI mass fraction of 57.65% and an I2 content of 0.03%.

[0023] Furthermore, the hydrogen iodide decomposition kinetics test method uses contact time t for characterization:

[0024] t = W c / F;

[0025] In the formula, W c The mass (kg) of catalyst packed for a single experiment is given, and F is the sum of the inlet molar flow rates of HI and H2O gases (in mol / s). Different packing masses of 0.5g, 1.18g, and 2.31g were used in the AC catalyst test; and different packing masses of 1.18g, 2.5g, and 5.2g were used in the Pt / Al2O3 catalyst test.

[0026] Furthermore, the hydrogen iodide decomposition kinetics test method uses HI solution as the feed liquid, and the HI reaction rate kinetic equation is derived as follows:

[0027]

[0028] Using an azeotropic HI solution as a raw material, a reaction mixture is obtained through vaporization. The partial pressures of each component gas can be expressed as:

[0029]

[0030] In the formula, The initial partial pressures of HI and I2 gases are respectively, and the equation is... The partial pressures of each component gas are replaced and eliminated. get:

[0031]

[0032] In the formula, and The specific values ​​can be calculated based on the components of the HI reagent and the experimental conditions. Further simplification yields:

[0033]

[0034] In the formula, K p It can be expressed by the following formula:

[0035]

[0036] Another object of the present invention is to provide a hydrogen iodide decomposition kinetic testing device based on the aforementioned hydrogen iodide decomposition kinetic testing method. The device includes: a push-pull injection pump for pushing hydrogen iodide solution to an HI vaporizer; an HI vaporizer for converting liquid hydrogen iodide solution into gas; a quartz reaction tube with a diameter of 12 mm for receiving gas from the HI vaporizer and vertically placing it in an electric heating furnace for catalytic reaction; an electric heating furnace for providing the necessary heat to drive the reaction; a condenser and gas-liquid separator for receiving the reaction gas flowing out of the reaction tube and performing condensation and gas-liquid separation; a tail gas absorption device for receiving and treating the gas separated from the gas-liquid separator to reduce environmental impact; and a thermal conductivity hydrogen analyzer for receiving and analyzing the gas separated from the gas-liquid separator to assess the reaction progress and results. Another object of the present invention is to provide a renewable energy kinetic testing method using the aforementioned hydrogen iodide decomposition kinetic testing device.

[0037] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0038] First, based on previous kinetic studies, this invention selects two different commercial catalysts, activated carbon and Pt-alumina, to conduct kinetic experiments on the HI decomposition reaction within a pressure range of 1 atm and a temperature range of 573-723 K, determining the corresponding kinetic parameters and obtaining reaction rate models for different commercial catalysts. Simultaneously, the two different commercial catalysts are applied to the reactor design process to analyze the impact of different types of catalysts on reactor performance.

[0039] Secondly, comparisons revealed that the apparent activation energy of HI on the AC catalyst surface obtained in this experiment was 39.9 kJ / mol, a value between 34.4 and 55.5 kJ / mol calculated by Oosawa and Favuzza, respectively. The apparent activation energy of HI on the Pt / γ-Al₂O₃ catalyst surface was 29.7 kJ / mol, close to the 27.6 kJ / mol calculated by Shindo's experiment. Therefore, the kinetic parameters obtained through this experimental method are reasonable, and the determination of these reaction kinetic parameters provides an experimental data basis for the design and application of HI decomposition reactors.

[0040] Third, the sulfur-iodine thermochemical cycle can directly decompose water into hydrogen and oxygen, which is a highly efficient and green hydrogen production method. The HI decomposition reaction is the key hydrogen production step in this cycle system. Researching how to efficiently utilize existing commercial catalysts to improve HI conversion and hydrogen yield is crucial for enhancing the thermal efficiency of the cycle system. This invention provides a HI decomposition reaction kinetic testing device and method, systematically introducing the testing device, experimental procedures, and data processing methods for kinetic experiments, providing methods and basis for subsequent related kinetic experimental research. The extension of this invention can be applied to the kinetic experimental research of commercial catalysts in the HI decomposition process. By testing the kinetic parameters of different commercial catalysts and conducting comparative studies, it is beneficial to gain a deeper understanding of the catalytic characteristics of different commercial catalysts, providing theoretical guidance for the next step of reactor design and industrial application.

[0041] The technical solution of this invention fills a technological gap in the industry both domestically and internationally:

[0042] Currently, there are limited kinetic tests and comparative studies on commercial HI decomposition catalysts. Furthermore, HI solution is often used as the feed solution in experimental tests, inevitably containing a small amount of I₂, which affects the accuracy of kinetic parameter measurements to some extent. There is a lack of universal and effective testing equipment and methods for reaction kinetic experiments under these conditions. This invention, considering the presence of a small amount of I₂ in the feed solution, derives the HI decomposition kinetic equation and systematically conducts kinetic tests on commercial catalysts. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the hydrogen iodide decomposition kinetics testing device provided in an embodiment of the present invention;

[0044] Figure 2 This is a flowchart of the hydrogen iodide decomposition kinetics test method provided in the embodiments of the present invention;

[0045] Figure 3 This is a schematic diagram illustrating the change of HI conversion rate with contact time at different temperatures using an activated carbon catalyst, provided in an embodiment of the present invention.

[0046] Figure 4 This is an Arrhenius diagram of HI on activated carbon catalyst provided in the embodiments of the present invention;

[0047] Figure 5 This is a schematic diagram illustrating the change in HI conversion rate with contact time at different temperatures using a Pt / Al2O3 catalyst, provided in an embodiment of the present invention.

[0048] Figure 6 This is an Arrhenius diagram of HI on a Pt / Al2O3 catalyst provided in the embodiments of the present invention;

[0049] Figure 7 This is a schematic diagram illustrating the effect of different feed solution HI ratios on HI conversion rate provided in this embodiment of the invention;

[0050] Figure 8 These are HI conversion curves for reactors filled with different catalysts provided in this embodiment of the invention.

[0051] Figure 9 These are the HI decomposition reaction rate curves provided in the embodiments of the present invention under different catalyst packing conditions in the reactor;

[0052] Figure 10 This is a physical diagram of the dynamic testing device provided in the embodiment of the present invention;

[0053] Figure 11 This is the dynamic test data acquisition interface provided in the embodiments of the present invention;

[0054] In the diagram: 1. Nitrogen tank; 2. Mass flow controller; 3. Bidirectional push-pull injection pump; 4. HI solution; 5. HI evaporator; 6. Quartz reaction tube; 7. Heating furnace; 8. Condenser; 9. Gas-liquid separator; 10. NaOH solution; 11. Silica gel; 12. Thermal conductivity hydrogen analyzer; 13. Mass flow meter. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] like Figure 1 As shown, the hydrogen iodide decomposition kinetics testing device provided in this embodiment of the invention comprises: a push-pull injection pump, an HI vaporizer, a quartz reaction tube, an electric heating furnace, a condenser and gas-liquid separator, a tail gas absorption device, and a thermal conductivity hydrogen analyzer; the catalytic reaction experiment is carried out in a quartz tube reactor with a diameter of 12 mm, and the reaction tube is placed vertically in the electric heating furnace.

[0057] The hydrogen iodide decomposition kinetics test method provided in this embodiment of the invention includes the following steps:

[0058] S101: Weigh a certain mass of catalyst sample using an electronic balance and fill it into the middle of the reaction tube. Fix it with high-purity quartz wool on the top and bottom sides.

[0059] S102: The HI solution is introduced into the HI evaporator using a two-way injection pump, and the vaporized HI gas is purged by N2 and enters the reaction tube together.

[0060] S103: After catalytic reaction in a fixed-bed reactor, the reaction mixture is first condensed by a condenser and then separated by a gas-liquid separator;

[0061] S104: Acidic gas impurities and water are removed by sodium hydroxide solution and silica gel, and finally only a mixture of N2 and H2 gas is allowed to enter the hydrogen analyzer. The H2 concentration at the outlet is measured using a thermal conductivity hydrogen analyzer.

[0062] Furthermore, the operating temperature in the second step is controlled above 150℃, the liquid feed rate is set to 0.05-0.35mL / min, and the N2 flow rate is 50-350mL / min.

[0063] In the embodiments of this invention, various data such as temperature, flow rate, pressure, and H2 concentration during the test can be monitored and collected in real time using the data acquisition system, with a data acquisition frequency of 1 second / time. After each change in the HI feed flow rate, the reaction process will undergo a period of change to reach an equilibrium state. When the collected hydrogen concentration is observed to remain unchanged within 15 minutes, the reaction system is considered to have reached a stable state. The H2 concentration and outlet gas flow rate at this time are recorded and used for subsequent data processing.

[0064] In this invention, the conversion rate of HI cannot be directly measured; it requires the collection of the gas flow rate Q at the outlet. V The H2 concentration C measured by the hydrogen analyzer H2 The calculation yields the following formula:

[0065]

[0066] In the formula, Q F Q is the feed rate (mL / min) of the HI solution. V w represents the total flow rate (mL / min) of N2 and H2 gases at the outlet. HI The density and mass fraction of the HI solution are M, respectively. HIThe molar mass of HI is given in g / mol. According to the technical specifications of the equipment provided by the manufacturer, the control accuracy of the push-pull syringe pump is ±0.5%, the measurement accuracy of the mass flow meter is ±1.0%, and the measurement accuracy of the hydrogen analyzer is ±2.0%. Based on the error propagation formula, the relative error of the HI conversion rate can be further analyzed and determined.

[0067]

[0068] Therefore, the relative error of HI obtained from a single measurement using the measurement data is 3.5%.

[0069] In this invention, two commercially available catalysts were used: activated carbon (AC) and alumina-supported platinum (Pt / Al2O3) catalyst. The activated carbon used was Cabot Norit's ROX 0.8, processed by steam activation followed by acid washing. The catalyst particles were cylindrical with a diameter of approximately 0.8 mm. The Pt / γ-Al2O3 catalyst was manufactured by Sigma-Aldrich, processed by impregnation and calcination, with a Pt loading of 0.5% and a particle size of 3.2 mm. The reagent used was a hydroiodic acid solution manufactured by Rhohn. Due to the oxidizing effect of oxygen in the air, a small amount of iodine was unavoidable in the solution. Before shipment, the HI, I2, and H2O components in the solution were titrated, yielding a HI mass fraction of 57.65% and an I2 content of 0.03%.

[0070] The reaction process needs to be tested under different catalyst loading masses, and the feed flow rate of the HI solution and the inlet flow rate of N2 are maintained in a certain ratio to ensure that the partial pressure of HI remains constant throughout the reaction. To facilitate comparison of results under different catalyst masses and feed rates, the contact time t is used to characterize each group of experiments.

[0071] t = W c / F (6)

[0072] In the formula W c The figure represents the mass (kg) of catalyst packed for a single experiment, and F represents the sum of the inlet molar flow rates (mol / s) of HI and H2O gases. Different packing masses of 0.5 g, 1.18 g, and 2.31 g were used in the AC catalyst test; and different packing masses of 1.18 g, 2.5 g, and 5.2 g were used in the Pt / Al2O3 catalyst test. The experimental test groups for different temperatures and catalyst masses are shown in Table 1. The symbol "○" indicates that experiments with different feed flow rates were completed under the corresponding temperature and catalyst mass group.

[0073] Table 1. Experimental test groupings under different temperatures and catalyst masses.

[0074]

[0075] In kinetic tests, HI azeotropic solutions are usually used as feed liquids, and a small amount of I2 is inevitably present in the solution. To better fit the kinetic test data and reflect the true performance of the catalyst, the kinetic equation for the HI decomposition reaction when the feed contains I2 is first derived, and then the reaction kinetic parameters are obtained by fitting the measured experimental data. Based on the Langmuir-Hinshelwood adsorption model, it is assumed that the HI decomposition process is a rate-determining step: (1) the adsorption of HI and H2O is molecular adsorption, and H and I are dissociative adsorption; (2) the rate-determining step is the decomposition of HI on the catalyst surface. From this, the HI reaction rate kinetic equation can be derived as follows:

[0076]

[0077] In the experiment, an HI azeotropic solution was used as a raw material. A reaction mixture was obtained through vaporization. Because the HI azeotropic solution contained a small amount of iodine impurities, a certain amount of gaseous iodine was present in the inlet component of the gas. Therefore, the partial pressures of each component gas can be expressed as:

[0078]

[0079] In the formula, These are the initial partial pressures of HI and I2 gases, respectively. Substitute the partial pressures of each component gas in equation (7) and eliminate... get:

[0080]

[0081] In the formula, and The specific values ​​can be calculated based on the components of the HI reagent and the experimental conditions. Further simplification yields:

[0082]

[0083] In the formula, K p It can be expressed by the following formula:

[0084]

[0085] Oosawa et al. used AC as a catalyst, and Shindo et al. used Pt / Al2O3 as a catalyst to conduct experimental studies on the decomposition of HI, and obtained the adsorption rate expressions for iodine respectively:

[0086]

[0087] Based on the technical solution of the HI decomposition kinetics experimental testing device and method, different commercial catalysts, reagents and instruments were selected to build an HI decomposition kinetics experimental platform, and experimental testing was carried out. The physical diagram of the testing device and the data acquisition process are as follows: Figure 10 , Figure 11 As shown.

[0088] The experimental data were fitted using the least squares method with the Matlab function "lsqnonlin". Table 2 lists the rate constant k values ​​at different temperatures obtained through fitting and the equilibrium constant K obtained through calculation. p And the adsorption term coefficient value b.

[0089] Table 2. Reaction rate constants, adsorption term coefficients, and equilibrium constants at different temperatures.

[0090]

[0091] Comparison of the results calculated by the kinetic model with experimental data values, for example Figure 3 As shown, the two results are in good agreement. At a certain temperature, the conversion rate of HI increases with increasing t, but the rate of increase decreases continuously. Because the reactants are easily adsorbed onto the catalyst in the initial stage of the reaction, the adsorption resistance is relatively small, resulting in a higher slope of conversion rate in the early stage. As the contact time increases, the slope of conversion rate tends to flatten. Simultaneously, HI is an endothermic reaction, and the HI conversion rate increases with increasing decomposition temperature.

[0092] Figures 4-6 The Arrhenius plot of the logarithm of the reaction rate constant ln k versus the reciprocal of the reaction temperature is used. By fitting a straight line using the least squares method to solve for the activation energy, the reaction rate constants for the two catalysts can be further determined as follows:

[0093]

[0094] To analyze the effect of different feed components on HI conversion, three different feed solutions with I2 / HI ratios were selected for testing, and the reaction temperature was maintained at 723K throughout the test. Figure 7 The figure shows the effect of different I₂ / HI ratios in the HI feed solution on the HI conversion rate. As the proportion of iodine in the feed solution increases, the HI conversion rate decreases significantly. Furthermore, the difference in HI conversion rate under different feed solutions increases with increasing contact time. This is because the presence of a large amount of iodine in the feed solution inhibits the HI decomposition reaction, and this inhibitory effect becomes more pronounced in the later stages of the reaction. The curves obtained using this kinetic model also show good agreement with the experimental data, fully verifying the accuracy of the kinetic parameters obtained through fitting.

[0095] Table 3 lists a comparison of the kinetic parameters for different HI decomposition reactions. The comparison reveals that the apparent activation energy of HI on the AC catalyst surface obtained in this experiment is 39.9 kJ / mol, which falls between the values ​​of 34.4 and 55.5 kJ / mol obtained by Oosawa and Favuzza, respectively. The apparent activation energy of HI on the Pt / γ-Al₂O₃ catalyst surface is 29.7 kJ / mol, close to the 27.6 kJ / mol obtained by Shindo's experiment. Therefore, the kinetic parameters obtained by this experimental method are reasonable, and the determination of these reaction kinetic parameters provides an experimental basis for the design and application of HI decomposition reactors.

[0096] Table 3 Comparison of kinetic parameters for different HI decomposition reactions

[0097]

[0098] The effects of different catalysts on reactor performance under the same parameters were analyzed. The reactor parameter settings are shown in Table 4. The influence of heat source temperature was ignored, and it was assumed that the heat source temperature changed linearly during the analysis, i.e., T a =600+200z / L.

[0099] Table 4 Reactor operating parameters

[0100]

[0101] Figure 8 The figure shows the HI conversion distribution curves in the reactor under different catalyst conditions. It can be observed from the figure that... At the specified location, the HI conversion rate in the reactor filled with AC activated carbon was lower than that of Pt / Al2O3. This indicates that at low temperatures below 640 K, the catalytic effect of Pt / Al2O3 is better than that of AC activated carbon. As the reaction temperature increases, the HI conversion rate in the AC activated carbon reactor begins to exceed that of Pt / Al2O3. Figure 9 The distribution curves of HI decomposition rate in the reactor under different catalyst conditions are shown. It can be seen that... At that location, the HI decomposition rate in the Pt / Al2O3 reactor was slightly higher than that in the AC activated carbon reactor. At this point, the HI decomposition rate in the activated carbon reactor gradually increases and reaches a relatively high peak decomposition rate. Therefore, Pt / Al2O3 is more suitable for low-temperature decomposition conditions, while activated carbon is more suitable as a catalyst for high-temperature decomposition conditions.

[0102] In this embodiment of the invention, the nitrogen tank 1 is connected to a mass flow controller 2 to control the flow rate of nitrogen. A bidirectional push-pull injection pump 3 delivers HI solution 4 to the HI evaporator 5. The HI evaporator 5 converts the solution into a gaseous state and transfers it to a quartz reaction tube 6. The quartz reaction tube 6 is placed in a heating furnace 7 for reaction. The reaction products are condensed by a condenser 8 and then separated by a gas-liquid separator 9. The liquid portion of the gas-liquid separator 9 is neutralized by a NaOH solution 10, and the gaseous portion is dried by silica gel 11. The dried gas is analyzed by a thermal conductivity hydrogen analyzer 12. All gas mass flow rates are measured and monitored by a mass flow meter 13.

[0103] The significant technological advancements brought about by the device provided in this embodiment of the invention include:

[0104] By using a combination of a bidirectional push-pull syringe pump 3 and a HI evaporator 5, the initiation and progress of the reaction can be controlled more accurately, resulting in more reliable kinetic data. Conducting the reaction in a quartz reaction tube 6 allows for completion at high temperature and high pressure, expanding the experimental applicability. Using a condenser 8 and a gas-liquid separator 9, gases and liquids can be effectively separated from the reaction products, enabling accurate measurement and analysis of the reaction products. Using a thermal conductivity hydrogen analyzer 12 and a mass flow meter 13 allows for real-time monitoring and analysis of the reaction progress, enabling timely adjustment of experimental conditions and improving experimental accuracy and efficiency.

[0105] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method of testing the decomposition kinetics of hydrogen iodide, characterized in that, The hydrogen iodide decomposition kinetics test method The method comprises the following steps: In the first step, an electronic balance is used to weigh the catalyst sample, which is then filled into the middle of the reaction tube, and high-purity quartz wool is used to fix the upper and lower sides; In the second step, a bidirectional injection pump is used to pass the HI solution into the HI evaporator, and the vaporized HI gas is blown into the reaction tube together with N2; In the third step, after the catalytic reaction in the fixed bed reactor, the reaction mixed gas is first condensed by the condenser and then separated in the gas-liquid separator; Fourth step, by sodium hydroxide solution and silica gel to remove acidic gas impurities and water, finally only allow N2 and H2 mixture gas into the hydrogen analyzer, using thermal conductivity type hydrogen analyzer to measure the H2 concentration at the outlet; under different catalyst filling mass and different reaction temperature, the test is carried out, and the feeding flow rate of HI solution and the N2 inlet flow rate keep constant proportion, the hydrogen concentration value under different reaction contact time is measured; based on the simplified kinetic equation, the experimental data is fitted by using the least square method and Matlab function "lsqnonlin"; the rate constant value k at different temperatures and the equilibrium constant K and the adsorption term coefficient value b are obtained by fitting and calculation through the fitting of experimental data p ​ The conversion of HI in the hydrogen iodide decomposition kinetic test method is calculated by collecting the gas flow rate Q V and the H2 concentration C measured by the hydrogen analyzer H2 The conversion of HI is calculated as follows: ； where Q F is the feed rate of the HI solution in mL / min, Q V is the total flow rate of N2and H2gases at the outlet in mL / min, and w HI are the density and mass fraction of the HI solution, respectively, M HI is the molar mass of HI in g / mol; The catalysts used in the hydrogen iodide decomposition kinetics test method are activated carbon AC and platinum on alumina catalyst Pt / γ-Al2O3, respectively. The activated carbon is processed by steam activation and then acid washing. The catalyst particles are cylindrical with a particle size of 0.8 mm. The Pt / γ-Al2O3 catalyst is processed by impregnation and calcination. The Pt loading mass fraction is 0.5%, and the particle size is 3.2 mm. The reagent used is hydroiodic acid solution, which has a mass fraction of 57.65% of HI and a content of 0.03% of I2. The HI azeotrope solution is used as the feed liquid in the hydrogen iodide decomposition kinetics test method, and the HI reaction rate kinetics equation is derived as follows: ； Using the HI azeotrope solution as the raw material, the reaction mixed gas is obtained by vaporization, and the partial pressure of each component gas is represented as follows: ； ； ； wherein , are the initial partial pressures of the gases HI and I2, respectively, and the partial pressures of the individual component gases in the formula are replaced and the resulting: ； wherein and The specific values are calculated from the HI reagent components and the test experimental conditions, which are , , which further simplifies to: ； In the formula, K p is expressed by the following equation: 。 2. The hydrogen iodide decomposition kinetics test method of claim 1, wherein, The liquid feed rate in the second step is set to 0.05-0.35 mL / min, and the flow rate of N2 is 50-350 mL / min.

3. The hydrogen iodide decomposition kinetics test method of claim 1, wherein, The temperature, flow rate, pressure, and H2 concentration data in the hydrogen iodide decomposition kinetics test method are monitored and collected in real time using a data acquisition system. The data acquisition frequency is 1 s / time. After changing the HI feed flow rate each time, the reaction process will change for a period of time to reach a steady state. When it is observed that the collected hydrogen concentration remains unchanged within 15 min, the reaction system reaches a stable state. The H2 concentration and outlet gas flow rate value at this time are recorded and used for later data processing.

4. The hydrogen iodide decomposition kinetics test method of claim 1 wherein, According to the error propagation formula, the relative error of the HI conversion rate is obtained as follows: ； Through the measurement data, the relative error of the HI conversion rate in a single measurement is 3.5%.

5. The hydrogen iodide decomposition kinetics test method of claim 1 wherein, The contact time t is used to represent the hydrogen iodide decomposition kinetics test method. ； wherein W c is the mass of catalyst charged for a single experiment, in kg, and F is the sum of the molar flow rates of the incoming H I and H 20 gases, in mol / s; during the AC catalyst tests, different charged masses of 0.5 g, 1.18 g, 2.31 g were used, respectively; during the Pt / γ- AI 20 3 catalyst tests, different charged masses of 1.18 g, 2.5 g, 5.2 g were used, respectively.

Images