In-situ reaction tank combining steady-state isotope transient kinetic analysis technology and infrared spectrum technology

Abstract

The invention belongs to the technical field of in-situ infrared spectrum characterization, and discloses a steady-state isotope transient kinetic analysis technology and infrared spectrum technology combined in-situ reaction tank, which comprises a reaction tank main body, a sample bracket and an accessory, due to the design of the sample bracket, gas enters the sample chamber from the gas inlet, is in contact with a sample immediately and then flows out from the gas outlet, so that the problem of gas vortex backmixing is solved; and the thermocouple is inserted into the sample bracket to be in close contact with the sample, so that the temperature of the sample is controlled at high precision, and the problems of large temperature gradient and slow time response are solved. The design of a single-side double-window-sheet structure is adopted, the inner-layer window sheet is close to the sample chamber to reduce dead volume, and the inner-layer window sheet is arranged in a heating area; the outer-layer window sheet is arranged in the cooling area so as to protect the in-situ reaction tank from being damaged by high temperature. The in-situ reaction tank provided by the invention can realize dynamic detection of species and products thereof on the surface of the catalyst under a steady-state condition by being combined with a steady-state isotope transient kinetic analysis technology and an infrared spectrum technology.

Description

Technical Field

[0001] This invention belongs to the field of in-situ infrared spectroscopy characterization technology, and relates to an in-situ reaction cell that combines steady-state isotope transient dynamics analysis (SSITKA) with infrared spectroscopy (FTIR). Background Technology

[0002] In-situ characterization techniques are widely used to study the reaction mechanisms of catalysts, which is of great significance for guiding the development of high-performance catalysts. However, most existing in-situ reaction tanks generally suffer from drawbacks such as large dead volume, large temperature gradient, gas vortex backmixing, and slow time response. This leads to most in-situ catalytic characterization studies being conducted during the transition from unsteady to steady state (or from steady to unsteady state), under which the reaction kinetics and even the reaction process differ significantly from those under steady-state reaction conditions (industrial production conditions). When the reaction reaches steady state, the transformation of surface species into products has reached dynamic equilibrium, presenting a static spectrum, making it difficult to observe the dynamic changes of species. Furthermore, under these conditions, perturbations of adsorbed species and the chemical environment surrounding the catalyst surface can also lead to behavioral characteristics different from those in steady state.

[0003] Therefore, there is an urgent need to design an in-situ reaction cell that can be combined with steady-state isotope transient kinetic analysis and infrared spectroscopy to study the dynamic changes of surface species and their relationship with products under steady-state reaction conditions. This is of great significance for accurately identifying the reaction mechanism and kinetic information of catalysts. Summary of the Invention

[0004] This invention provides an in-situ reaction cell that combines Steady-State Isotope Transient Kinetic Analysis (SSITKA) with Fourier Transient Infrared Spectroscopy (FTIR), overcoming the common drawbacks of most reaction cells, such as large dead volume, large temperature gradient, gas vortex backmixing, and slow time response. This allows for the simultaneous dynamic detection of catalyst surface species and their products under steady-state reaction conditions, enabling precise identification of the catalyst's reaction mechanism and kinetic information.

[0005] The technical solution of this invention:

[0006] An in-situ reaction cell combining steady-state isotope transient dynamics analysis with infrared spectroscopy mainly consists of a reaction cell body 17, a sample holder 7, and accessories. The reaction cell body 17 includes an inlet channel 1, an outlet channel 2, a cooling pipe 3, and a heating wire 4. The sample holder 7 is composed of a hollow metal ring 5, which has slots for the inlet channel 1, the outlet channel 2, and a thermocouple 8. The accessories include a thicker inner columnar crystal window 9, a thinner outer columnar crystal window 10, a PEEK ring 11, a Kalrez O-ring 12, a metal ring 13, an airtightness adjusting nut 14, a polytetrafluoroethylene ring 15, and a window adjusting nut 16.

[0007] A circular sample 6 is installed in a sample holder 7, ensuring that the size of the sample 6 is consistent with the size of the hollow area of ​​the sample holder 7; the sample holder 7 is installed at the center of the reaction cell body 17, ensuring that the slots of the air inlet channel 1, air outlet channel 2 and thermocouple 8 on the sample holder 7 are aligned with the mounting holes of the air inlet channel 1, air outlet channel 2 and thermocouple 8 on the reaction cell body 17; the thermocouple 8 is inserted until it reaches the slot of the thermocouple 8 on the sample holder 7, fixing the position of the sample holder 7 and ensuring that the end of the thermocouple 8 touches the sample 6;

[0008] The thicker inner columnar crystal window 9 is placed close to the sample holder 7 to eliminate dead volume; the heating wire 4 is wrapped around the outside of the reaction cell body 17 to uniformly heat the sample 6, and ensures that the heating area does not exceed the length of the thicker inner columnar crystal window 9.

[0009] The thinner columnar crystal window 10 on the outer side is placed close to the thicker columnar crystal window 9 on the inner side. The cooling pipe 3 is wrapped around the outside of the reaction tank body 17, covering the thinner columnar crystal window 10 on the outer side, forming a cooling area.

[0010] A PEEK ring 11, a Kalrez O-ring 12, and a metal ring 13 are sequentially installed from the inside to the outside on the outer surface of the thinner columnar crystal window 10, and then tightened and fixed by an airtight adjusting nut 14. The airtight adjusting nut 14 has a hollow structure, and a polytetrafluoroethylene ring 15 is installed in close contact with the thinner columnar crystal window 10. It is then tightened and fixed by a window adjusting nut 16. The window adjusting nut 16 has a hollow structure, which is used for the passage of infrared light.

[0011] According to experimental requirements, the materials selected for columnar crystal windows include potassium bromide, calcium fluoride, and zinc selenide.

[0012] This in-situ reaction cell, which combines steady-state isotope transient dynamics analysis (SSITKA) with infrared spectroscopy, can be matched with various models of Fourier transform infrared spectrometers.

[0013] The beneficial effects of this invention are:

[0014] This invention addresses the shortcomings of most in-situ reaction tanks, such as large dead volume, large temperature gradient, gas vortex backmixing, and slow time response. It enables the simultaneous dynamic detection of catalyst surface species and their products under steady-state reaction conditions by combining steady-state isotope transient kinetic analysis (SSITKA) and infrared spectroscopy, thereby accurately identifying the reaction mechanism and kinetic information of the catalyst. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view of an in-situ reaction cell used in Example 1, which combines steady-state isotope transient dynamics analysis (SSITKA) with infrared spectroscopy.

[0016] Figure 2 This is an overall view of the in-situ reaction cell used in Example 1, which combines steady-state isotope transient dynamics analysis (SSITKA) with infrared spectroscopy.

[0017] Figure 3 In Example 2, the feed gas to the catalyst comes from... 12 CO2 / H2 / Ar switch to 13 In-situ infrared spectrum of CO2 + H2 over time.

[0018] Figure 4 In Example 3, the feed gas to the catalyst is generated within 0 seconds from... 12 CO2 / H2 / Ar switch to 13 Normalized mass spectrometry (MS) response of gases in CO2 / H2 effluent.

[0019] In the figure: 1. Inlet channel, 2. Outlet channel, 3. Cooling pipe, 4. Heating wire, 5. Hollow metal ring, 6. Sample, 7. Sample holder, 8. Thermocouple, 9. Inner thicker columnar crystal window, 10. Outer thinner columnar crystal window, 11. PEEK ring, 12. Kalrez O-ring, 13. Metal ring, 14. Air tightness adjustment nut, 15. PTFE ring, 16. Optical window adjustment nut, 17. Reaction cell body. Detailed Implementation

[0020] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0021] Example 1

[0022] like Figure 1-2As shown, an in-situ reaction cell combining steady-state isotope transient dynamics analysis with infrared spectroscopy mainly consists of a reaction cell body 17, a sample holder 7, and accessories. The reaction cell body 17 includes an inlet channel 1, an outlet channel 2, a cooling pipe 3, and a heating wire 4. The sample holder 7 is composed of a hollow metal ring 5, which has slots for the inlet channel 1, the outlet channel 2, and a thermocouple 8. The accessories include a thicker inner columnar crystal window 9, a thinner outer columnar crystal window 10, a PEEK ring 11, a Kalrez O-ring 12, a metal ring 13, an airtightness adjusting nut 14, a polytetrafluoroethylene ring 15, and a window adjusting nut 16. The specific assembly steps are as follows: First, the sample 6 is pressed into a circular shape and inserted into the sample holder 7, ensuring that the size of the sample 6 is consistent with the size of the hollow area of ​​the sample holder 7. Then, the sample holder 7 is installed at the center of the reaction cell body 17, ensuring that the inlet channel 1, outlet channel 2, and thermocouple 8 slots on the sample holder 7 are aligned with the inlet channel 1, outlet channel 2, and thermocouple 8 mounting holes on the reaction cell body 17. This allows gas to enter, contact the sample 6, and then flow out, avoiding gas turbulence. Next, the thermocouple 8 is inserted into the reaction cell body 17, extending to the sample holder 7, to fix the position of the sample holder 7 and ensure that the end of the thermocouple 8 touches the sample 6, guaranteeing high-precision temperature detection of the sample 6 and avoiding large temperature gradients and slow temperature-time response on the sample 6 surface. After placing the sample holder 7 at the center of the reaction cell body 17, the thicker inner columnar crystal window 9 is placed tightly against the sample holder 7 to eliminate dead volume. Furthermore, the heating wire 4 is wound around the outside of the reaction cell body 17 to uniformly heat the sample 6, ensuring that the heating area does not exceed the length of the thicker inner columnar crystal window 9. Then, the thinner outer columnar crystal window 10 is placed tightly against the thicker inner columnar crystal window 9, ensuring that the thinner outer columnar crystal window 10 is completely within the cooling zone. The cooling zone consists of cooling pipes 3 wrapped around the outside of the reaction tank body 17, covering the thinner outer columnar crystal window 10. Depending on the specific experimental requirements, the columnar crystal window material can be potassium bromide, calcium fluoride, or zinc selenide, etc. A PEEK ring 11, a Kalrez O-ring 12, and a metal ring 13 are sequentially installed from the inside out on the outer surface of the thinner outer columnar crystal window 10, and then tightened and fixed using an airtightness adjusting nut 14. The airtightness adjusting nut 14 is a hollow structure, and a polytetrafluoroethylene ring 15 is installed in close contact with the thinner outer columnar crystal window 10, and then tightened and fixed using a window adjusting nut 16. The window adjusting nut 16 is also a hollow structure, allowing infrared light to pass through.

[0023] Example 2

[0024] The in-situ reaction cell using a combination of steady-state isotope transient kinetic analysis (SSITKA) and infrared spectroscopy, as described in Example 1, was used to analyze the feed gas from... 12CO2 / H2 / Ar converts to 13 In-situ infrared spectroscopy was performed to investigate the time-dependent changes of CO2 + H2. 40 mg of Pd / Al2O3 catalyst was compressed into tablets and placed in a reaction vessel. The catalyst was first reduced at 500 °C in 10% H2 / 90% He for 2 hours, then switched to He for 1 hour of purging. The temperature was then lowered to 260 °C, and the background spectrum was collected. Subsequently, the catalyst was purged with... 12 When the infrared spectral peaks of the CO2 / H2 / Ar gas no longer change, switch the gas to 13 CO2 + H2, H can be observed by observing the change in peak position. 12 COO* Species towards H 13 The phenomenon of COO* species transformation, such as Figure 3 As shown.

[0025] Example 3

[0026] The in-situ reaction cell using a combination of steady-state isotope transient kinetic analysis (SSITKA) and infrared spectroscopy, as described in Example 1, was used to analyze the feed gas from... 12 CO2 / H2 / Ar converts to 13 In-situ infrared spectroscopy was performed to investigate the time-varying effects of CO2 + H2. 40 mg of Pd / Al2O3 catalyst was compressed into tablets and placed in a reaction vessel. The catalyst was first reduced at 500°C in 10% H2 / 90% He for 2 hours, then switched to He for 1 hour of purging. The temperature was then lowered to 260°C, and the background spectrum was collected. The corresponding in-situ infrared spectra were recorded in Example 2. Figure 3 Here we used an external mass spectrometer to record the feed gas flow from [source] in 0 seconds. 12 CO2 / H2 / Ar switch to 13 Normalized mass spectrometry (MS) response of gases in the effluent after CO2 / H2. For example... Figure 4 As shown, we observed 12 CO2 disappears almost as quickly as Ar, which indicates that 12 The interaction between CO2 and the catalyst and reactor wall is weak, which also indicates that our in-situ reaction tank has a small dead volume and a fast response time. Meanwhile, 13 The concentration of CO2 signal also increases accordingly, while carbon dioxide ( 12 CO2+ 13 The concentration and conversion rate of CO2 remained constant during the switching process. Furthermore, we found... 12 CO decay signal and 13The rising CO signal crosses at y = 0.5, indicating that the carbon monoxide formation rate remains constant. This symmetrical reaction suggests that the steady state of the catalyst surface remains undisturbed during the switching process. Combined with Example 2, this further demonstrates that our in-situ reaction tank and the combined use of steady-state isotope transient kinetic analysis (SSITKA) with infrared spectroscopy can achieve simultaneous dynamic detection of catalyst surface species and their products under steady-state reaction conditions.

Claims

1. An in-situ reaction cell combining steady-state isotope transient kinetic analysis technology with infrared spectroscopy, characterized in that, The in-situ reaction cell mainly consists of the reaction cell body (17), the sample holder (7), and accessories; The reaction tank body (17) includes an inlet channel (1), an outlet channel (2), a cooling pipe (3), and a heating wire (4); the sample holder (7) is composed of a hollow metal ring (5); the hollow metal ring (5) is provided with slots for the inlet channel (1), the outlet channel (2), and the thermocouple (8); the accessories include a thicker inner columnar crystal window (9), a thinner outer columnar crystal window (10), a PEEK ring (11), a Kalrez O-ring (12), a metal ring (13), an airtightness adjusting nut (14), a polytetrafluoroethylene ring (15), and a window adjusting nut (16).

2. The in-situ reaction cell combining steady-state isotope transient dynamics analysis technology with infrared spectroscopy as described in claim 1, characterized in that, A circular sample (6) is installed in a sample holder (7) to ensure that the size of the sample (6) is consistent with the size of the hollow area of ​​the sample holder (7); the sample holder (7) is installed at the center of the reaction cell body (17) to ensure that the slots of the air inlet channel (1), air outlet channel (2) and thermocouple (8) on the sample holder (7) are aligned with the mounting holes of the air inlet channel (1), air outlet channel (2) and thermocouple (8) on the reaction cell body (17); the thermocouple (8) is inserted directly into the slot of the thermocouple (8) on the sample holder (7) to fix the position of the sample holder (7) and to ensure that the end of the thermocouple (8) touches the sample (6); The thicker inner columnar crystal window (9) is placed close to the sample holder (7) to eliminate dead volume; the heating wire (4) is wrapped around the outside of the reaction cell body (17) to uniformly heat the sample (6) and ensure that the heating area does not exceed the length of the thicker inner columnar crystal window (9); The thinner columnar crystal window (10) on the outside is placed close to the thicker columnar crystal window (9) on the inside. The cooling pipe (3) is wrapped around the outside of the reaction tank body (17) and covers the thinner columnar crystal window (10) on the outside to form a cooling area. On the outer surface of the thinner columnar crystal window (10) on the outside, a PEEK ring (11), a Kalrez O-ring (12) and a metal ring (13) are installed sequentially from the inside to the outside, and then tightened and fixed by an airtight adjusting nut (14); The airtightness adjusting nut (14) is a hollow structure. A polytetrafluoroethylene ring (15) is installed close to the outer thin columnar crystal window (10) of the hollow structure, and then tightened and fixed by the window adjusting nut (16). The window adjusting nut (16) is a hollow structure, and the hollow structure is used for infrared light to pass through.

3. The in-situ reaction cell combining steady-state isotope transient dynamics analysis technology with infrared spectroscopy as described in claim 1, characterized in that, The columnar crystal window can be made of potassium bromide, calcium fluoride, or zinc selenide.

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