A low dead volume gas-solid in-situ cell suitable for in-situ transmission infrared spectroscopy characterization

Abstract

The present application relates to a kind of low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization, including in-situ cell shell, reaction tube, two-section liner, first four-way sleeve, second four-way sleeve, reaction tube is through the mounting hole;Two-section liner is worn in the reaction tube, and catalyst after tabletting is clamped between two-section liner, and there is gap between the liner and reaction tube;First four-way sleeve first interface is connected with the reaction tube, and first four-way sleeve second interface is sealed and is inserted with thermocouple, and first four-way sleeve third interface is equipped with first optical window, and first four-way sleeve third interface is gas inlet, and second four-way sleeve third interface is equipped with second optical window, and second four-way sleeve fourth interface is gas outlet.Compared with prior art, the present application has the advantages of low internal dead volume, easy to operate, so the average residence time of gas is low, so that the in-situ spectroscopic study of gas-solid phase reaction has higher time resolution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of instrumental analysis, in particular to a low dead volume gas-solid in-situ cell suitable for in-situ transmission infrared spectroscopy characterization. BACKGROUND

[0002] Gas-solid phase catalytic reaction is a common type of reaction in chemical industry. Under reaction conditions, adsorption, reaction and desorption of gas on solid sample are important steps of gas-solid phase catalytic reaction. The atomic structure of solid sample itself dynamically changes under reaction conditions, which derives a series of key scientific problems such as formation rule of catalyst active center, structure-activity relationship of catalytic reaction and catalyst deactivation mechanism. In-situ transmission infrared technology can play a great role in studying the mechanism route of different reactions; in addition, adsorption of various different probe molecules such as CO and CO2 can also be used to indirectly analyze the structure of the surface. Compared with diffuse reflectance infrared, transmission is to obtain the absorption rate of the sample by detecting the transmitted light. Transmission method is closest to the principle of infrared absorption, and basically does not need accessories or only needs a simple clamp, so the spectrum is not easily disturbed, and therefore many standard spectra are obtained by transmission method.

[0003] The infrared reactor is limited by factors such as the size of the spectrometer, the detection method and the reaction conditions, so it needs to be reasonably designed. Among them, the residence time of the gas material should be as small as possible, so as to reduce back mixing diffusion, so that the environment of the catalyst responds quickly to the change of the reaction condition, not only close to the real reaction condition, but also can realize the research of fast transient process. In order to reduce the residence time of the material, it can be realized by increasing the operating gas velocity or reducing the dead volume of the in-situ cell, but the operating gas velocity should not be too high, otherwise it will cause the increase of convective heat loss and the non-uniformity of the temperature in the cell. Therefore, it is crucial to design an in-situ transmission reactor with as low dead volume as possible. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art, and to provide a low dead volume gas-solid in-situ cell suitable for in-situ transmission infrared spectroscopy characterization. The in-situ cell has the advantages of low internal dead volume and simple operation, so the average residence time of the gas is low, and the in-situ spectroscopy research of gas-solid phase reaction has higher time resolution.

[0005] The purpose of the present application can be realized by the following technical scheme:

[0006] The purpose of the present application is to provide a low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization, characterized in that it comprises an in-situ cell shell, a reaction tube, two section liners, a first four-way sleeve and a second four-way sleeve, wherein specifically:

[0007] The in-situ cell shell is provided with a mounting hole in the axial direction, and a heating module is arranged in the in-situ cell shell.

[0008] The reaction tube penetrates through the mounting hole, so that both sides of the reaction tube are arranged outside the in-situ cell shell.

[0009] Two sections of lining pipes are arranged in the reaction tube, and the catalyst after tabletting is clamped between the two sections of lining pipes, and there is a gap between the lining pipes and the reaction tube.

[0010] The first four-way sleeve is connected with the reaction tube at a first interface, a thermocouple is inserted and sealed at a second interface, a first optical window is arranged at a third interface, and the third interface is a gas inlet.

[0011] The second four-way sleeve is connected with the reaction tube at a first interface, a vacuum pump is connected at a second interface, a second optical window is arranged at a third interface, and a fourth interface is a gas outlet.

[0012] Further, the first four-way sleeve and the second four-way sleeve are both cross-shaped sleeves.

[0013] Further, the third interface of the first four-way sleeve, the reaction tube and the third interface of the second four-way sleeve are coaxial, thereby forming a straight-line transmission channel for in-situ transmission infrared spectroscopy.

[0014] Further, the first optical window and the second optical window are respectively provided with an emission module and a receiving module corresponding to the in-situ transmission infrared spectroscopy.

[0015] Further, the material of the first optical window and the second optical window is selected from one of potassium bromide, zinc selenide and calcium fluoride.

[0016] Further, the heating module is a heating tungsten wire arranged in the in-situ cell shell, thereby achieving heating of the internal space of the reaction tube.

[0017] Further, the thermocouple is inserted from the second interface of the first four-way sleeve and the end thereof extends into the position of the catalyst after tabletting.

[0018] Further, a DCS temperature control module arranged outside the in-situ cell shell is further included, the DCS temperature control module is electrically connected with the thermocouple and the heating tungsten wire, the DCS temperature control module outputs a current with a corresponding power to the heating tungsten wire based on a preset temperature and a real-time temperature obtained by the thermocouple.

[0019] Further, the material of the in-situ cell shell is aluminum, and the materials of the first four-way sleeve and the second four-way sleeve are 316 stainless steel.

[0020] Further, the material of the reaction tube is quartz tube or stainless steel tube.

[0021] The material of the lining tube is quartz tube.

[0022] Compared with the prior art, the present application has the following technical advantages:

[0023] (1) The in-situ cell in the technical solution has a low internal dead volume, a low residence time of gas material and a low degree of back mixing diffusion, because the lining tube has a similar inner diameter to the reaction tube and the gas flow volume is small, so that the in-situ cell has a faster dynamic response to changes in reaction conditions, and is more conducive to the study of fast transient reactions.

[0024] (2) The in-situ cell in the technical solution can be selectively connected to a vacuum pump and a back pressure valve to realize the regulation of low pressure and high pressure, thereby expanding the application range of the in-situ cell, and enabling the in-situ cell to be applied in a wider pressure range.

[0025] (3) The heating tungsten wire thermocouple in the in-situ cell in the technical solution is connected to a DCS temperature control module, and the thermocouple probe is on the surface of the catalyst, so that the real-time and accurate control of the bed temperature can be better realized.

[0026] (4) The in-situ cell in the technical solution is simple in design and does not need an external circulating water cooling system, so that the operation is more convenient. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a split view of the low dead volume gas-solid in-situ cell suitable for in-situ transmission infrared spectroscopy characterization in the present application;

[0028] Figure 2 is a three-view schematic diagram of the in-situ cell as a whole in the present application;

[0029] Figure 3 is a catalyst loading method of the reaction tube (quartz tube or stainless steel tube) in the present application.

[0030] Figure 4 is a temperature control schematic diagram of the thermocouple and heating tungsten wire cooperating with the DCS temperature control module in the present application.

[0031] Figure 5 is an infrared spectrum obtained by testing the catalyst at different reaction times.

[0032] 1, in-situ cell shell, 2, reaction tube, 3, pressed catalyst, 4, lining tube, 5, matching sleeve (four-way), 6, thermocouple, 7, DCS temperature control module, 8, heating tungsten wire. DETAILED DESCRIPTION

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0034] The purpose of this invention is to provide a low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization, characterized by comprising an in-situ cell shell 1, a reaction tube 2, two liner sections 4, a first four-way ferrule 5-1, and a second four-way ferrule 5-2, wherein specific details are provided below. Figures 1 to 4 .

[0035] In specific implementation, the in-situ pool shell 1 has an axially oriented mounting hole, and a heating module is provided in the in-situ pool shell 1; the reaction tube 2 passes through the mounting hole, so that both sides of the reaction tube 2 are placed outside the in-situ pool shell 1; two liner tubes 4 are inserted into the reaction tube 2, and the tableted catalyst 3 is clamped between the two liner tubes 4. Since the diameter of the liner tube is smaller than that of the reaction tube, and the design of the four-way ferrule allows the liner tube to be fixed in the center of the reaction tube, because the interface of the four-way ferrule is a conical structure, the diameter of the reaction tube 2 is slightly different from that of the liner tube, which can be abutted against the conical structure of the four-way ferrule, and a hard metal abutment seal is achieved by external fasteners. Therefore, there is a gap between the liner tube 4 and the reaction tube 2.

[0036] In specific implementation, the first four-way ferrule 5-1 has a first interface connected to the reaction tube 2, a second interface sealed and fitted with a thermocouple 6, a third interface with a first optical window, and an air inlet.

[0037] In specific implementation, the second four-way ferrule 5-2 has a first interface connected to the reaction tube 2, a second interface connected to a vacuum pump, a third interface with a second optical window, and a fourth interface as an outlet. Both the first four-way ferrule 5-1 and the second four-way ferrule 5-2 are cross-shaped ferrules. That is, the two opposing ferrule openings are coaxial, and the two axes are perpendicular to each other. The third interface of the first four-way ferrule, the reaction tube 2, and the third interface of the second four-way ferrule are coaxial, thus forming a linear transmission channel for in-situ transmission infrared spectroscopy. The first and second optical windows are respectively equipped with an in-situ transmission infrared spectroscopy transmitting module and a receiving module.

[0038] In specific implementation, the heating module is a tungsten wire 8 located inside the in-situ pool shell 1, thereby heating the internal space of the reaction tube 2. Thermocouple 6 is inserted through the second interface of the first four-way fitting, with its end extending into the position of the catalyst 3 after tableting.

[0039] In practical implementation, the in-situ pool in this technical solution also includes a DCS temperature control module located outside the in-situ pool shell 1. The DCS temperature control module is electrically connected to both the thermocouple 6 and the heating tungsten wire 8. Based on a preset temperature and the real-time temperature obtained by the thermocouple 6, the DCS temperature control module outputs a current with corresponding power to the heating tungsten wire 8. The DCS temperature control module is a readily available module purchased directly, and its structure will not be described in detail.

[0040] In terms of specific material selection, the materials for the first and second optical windows are selected from one of potassium bromide, zinc selenide, and calcium fluoride.

[0041] The outer shell 1 of the in-situ pool is made of aluminum, and the first four-way fitting 5-1 and the second four-way fitting 5-2 are made of 316 stainless steel. The reaction tube is made of quartz tube or stainless steel tube; the liner 4 is made of quartz tube.

[0042] In practical application, the specific implementation method of the low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization in this technical solution is as follows: First, the lower end liner 4 is placed into the reaction tube 2. Then, the tableted catalyst 3 is placed into the reaction tube 2, and the upper end liner 4 is added on top. This fixes the catalyst, and the use of the liner allows gas to pass through the gap between the liner 4 and the reaction tube 2. Then, the reaction tube is installed into the outer shell 1 of the in-situ cell, and matching four-way clamps are connected to both ends.

[0043] According to the experimental requirements, selectively connect a vacuum pump and a back pressure valve to the corresponding four-way fitting as shown in the diagram to control the pressure. Insert thermocouple 6 into the corresponding four-way fitting as shown in the diagram and connect the DCS temperature control module 7, and install the required window on the optical window. Finally, introduce the gaseous reactants into the in-situ cell through the gaseous reactant inlet, set the required reaction temperature and heating rate through the DCS temperature control module 7, and heat the catalyst bed through the heating tungsten wire 8; detect the signal of the reaction system to obtain information on the catalyst, reactants, intermediates, and products in the system.

[0044] For in-situ infrared spectroscopy testing, taking the synthesis of methanol catalyzed by the copper catalyst Cu / Al2O3 supported on alumina as an example, the matching ferrule and optical window were connected, a KBr material window was inserted, and infrared spectroscopy was used to test the reaction. Before formal evaluation, the Cu / Al2O3 catalyst powder was first pressed into tablets. The temperature of the catalyst bed was raised to 300℃ using the DCS temperature control module, and 60% H2 / N2 activation gas with a flow rate of 30 mL / min was introduced for activation. The activation gas entered the gas chamber through the gas inlet of the left ferrule, passed through the Cu / Al2O3 catalyst placed in the reaction tube, and flowed out through the gas outlet of the right ferrule.

[0045] After 0.5 hours of activation, the catalyst bed temperature was lowered to 200℃ using the DCS temperature control module. A mixture of carbon dioxide, hydrogen, and argon in a specific ratio was introduced at a flow rate of 30 ml / min. Infrared spectroscopy analysis of the catalyst was performed at regular intervals to obtain catalyst surface information. (See [link to relevant documentation]). Figure 5 .

[0046] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization, characterized in that, include: The in-situ pool shell (1) has mounting holes along the axial direction and a heating module is provided in the in-situ pool shell (1); The reaction tube (2) passes through the mounting hole, so that both sides of the reaction tube (2) are placed outside the in-situ pool shell (1); Two liner tubes (4) are inserted into the reaction tube (2). The tableted catalyst (3) is sandwiched between the two liner tubes (4). There is a gap between the liner tubes (4) and the reaction tube (2). The inner diameters of the liner tubes and the reaction tube are similar, and the gas flow volume is also small. The first four-way ferrule (5-1) has a first interface connected to the reaction tube (2), a second interface sealed and fitted with a thermocouple (6), a third interface provided with a first optical window, and a third interface serving as an air inlet. The second four-way ferrule (5-2) has a first interface connected to the reaction tube (2), a second interface connected to the vacuum pump, a third interface with a second optical window, and a fourth interface as an outlet. The third interface of the first four-way ferrule, the reaction tube (2), and the third interface of the second four-way ferrule are coaxial, thereby forming a linear transmission channel for in-situ transmission infrared spectroscopy. The first optical window and the second optical window are respectively provided with an in-situ transmission infrared spectrum emission module and a receiving module on each side; The thermocouple (6) is inserted from the second interface of the first four-way ferrule and its end extends into the position of the catalyst (3) after the tablet is pressed. It also includes a DCS temperature control module located outside the in-situ pool shell (1). The DCS temperature control module is electrically connected to both the thermocouple (6) and the heating tungsten wire (8). The DCS temperature control module outputs a current with corresponding power to the heating tungsten wire (8) based on the preset temperature and the real-time temperature obtained by the thermocouple (6).

2. The low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization according to claim 1, characterized in that, Both the first four-way card sleeve (5-1) and the second four-way card sleeve (5-2) are cross-shaped card sleeves.

3. The low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization according to claim 1, characterized in that, The material of the first optical window and the second optical window is selected from one of potassium bromide, zinc selenide, and calcium fluoride.

4. The low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization according to claim 1, characterized in that, The heating module is a heating tungsten wire (8) located inside the shell (1) of the in-situ pool, thereby achieving heating of the internal space of the reaction tube (2).

5. A low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization according to claim 1, characterized in that, The material of the in-situ pool shell (1) is aluminum, and the materials of the first four-way sleeve (5-1) and the second four-way sleeve (5-2) are 316 stainless steel.

6. A low dead volume gas-solid in-situ cell for in-situ transmission infrared spectroscopy characterization according to claim 1, characterized in that, The reaction tube is made of quartz or stainless steel. The liner (4) is made of quartz tube.

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