RU2791994C1 - Cell for x-ray spectroscopic diagnostics of liquid-phase samples in a controlled atmosphere under high pressures and temperatures in the operando mode - Google Patents

Abstract

FIELD: testing.

SUBSTANCE: area of application: for X-ray spectroscopic diagnostics of liquid-phase samples. Substance of the invention consists in the cell for X-ray spectroscopic diagnostics of liquid-phase samples containing a hollow body with the upper surface thereof equipped with a protrusion wherein a cup with the test sample is installed, made of a polymer non-radiopaque material and equipped with a ledge in the upper part thereof with the outer equal to the outer diameter of the protrusion; a cover rigidly connected to the body and made with holes for the installation of gas supply tubes; a hole is made on the side surface of the body, with a window made of a non-radiopaque material and tightly adjacent to the cup wall installed therein; a securing element with a central hole located, on top of the window and rigidly connected to the side wall of the body; heating elements located in the body channels; and a temperature sensor located in the hole of the body.

EFFECT: possibility of X-ray spectroscopic diagnostics of liquid samples in the operando mode under high temperatures and pressure of the gaseous medium.

6 cl, 1 dwg

Description

The invention relates to the field of analysis of the structure of materials under controlled conditions using an X-ray source, in particular to a cell for X-ray spectral diagnostics of liquid-phase samples in a controlled atmosphere at high pressures and temperatures in operando mode.

The closest in execution and functionality are the cell designs in patent documents No. 190702, No. 173869 and No. KR20200029262.

The cell for spectral diagnostics according to RF patent No. 190702 is intended for the study of materials for catalysis. It has the possibility of supplying gases, as well as heating and controlling the temperature of the sample. The cell allows measurement of X-ray absorption spectra, IR transmission spectra, as well as X-ray fluorescence spectra and IR diffuse reflectance spectra of samples in a controlled atmosphere in operando mode. This possibility is ensured by the presence in the case of windows made of transparent for IR and/or X-ray radiation. However, the cell according to RF patent No. 190702 is intended only for samples in solid or powder form, and there is no possibility to study liquid samples and solutions, as well as chemical reactions in them.

The cell for laboratory x-ray spectral diagnostics according to RF patent No. 173869 is also intended for analyzing the structure of materials under controlled conditions using x-ray sources due to the presence of windows made of x-ray transparent material in the cell. In addition, the cell can be connected to a gas line for evacuation or exposure of the sample to any gas or gas system. The disadvantages of the well-known cell according to the patent of the Russian Federation No. 173869 include the possibility of studying only solid samples. In addition, the cell according to the patent of the Russian Federation No. 173869 No. 173869 does not have a built-in possibility of heating and controlling the sample temperature. Another important difference according to the patent of the Russian Federation No. 173869 is that the design of the windows and the material of the case (glass) do not allow creating a high pressure of the gas atmosphere in the cell.

The electrochemical flow cell according to patent No. KR20200029262 is designed to study samples in a liquid electrolyte flow. The cell design uses a similar concept of X-ray transparent windows in the cell body to enable in situ and operando examination of samples by X-ray absorption spectroscopy. Described in the analogue design allows you to create a flow of liquid electrolyte around located in the cell of the investigated electrodes, to which there is the possibility of electrical connection. However, this cell does not have the ability to supply gases to the samples under study and is essentially electrochemical, that is, it is designed to study solid samples of electrode materials and chemical processes in them that occur under the action of an electric current in a liquid electrolyte medium, and not to study the actual liquid-phase samples and solutions. In addition, it is not possible to carry out studies under high pressure in this cell.

From the prior art, the authors know that high-temperature operando studies of liquid-phase samples and reactions in them that do not require high pressures are usually carried out in vessels made of conditionally X-ray transparent heat-resistant material, for example, quartz glass, polypropylene, Teflon. In the case of reactions at high operando pressures, studies were not carried out at all (that is, the reaction products were studied separately under normal conditions after it had taken place), or in some cases home-made modified factory chemical reactors were used, which were not originally intended for X-ray studies.

The technical problem of the claimed invention is the creation of a device that makes it possible to carry out X-ray spectral diagnostics of liquid samples in operando mode at high temperatures and pressure of the gaseous medium.

Using the developed cell design, it is possible to study liquid samples (for example, homogeneous catalysts) by X-ray absorption spectroscopy (for example, using synchrotron radiation) in the fluorescence output mode directly in the course of chemical reactions (in the operando mode). In addition, it is possible to set and control the required (required) temperature of the sample in the range from ambient temperature to 300 °C, as well as to maintain an increased pressure of the gaseous medium above the sample up to 50 bar.

The technical result is the ability to obtain the most reliable data on the local atomic and electronic structure of liquid samples and the dynamics of its change directly in the course of chemical reactions, for example, homogeneous catalysis reactions occurring at high temperature and pressure, which will lead to the improvement of existing chemical systems, for example, increasing the durability of catalysts and their efficiency, accelerating chemical reactions and increasing the yield and purity of the reaction product, as well as developing new systems based on them with improved quantitative and qualitative characteristics, thanks to a deep understanding of the mechanisms of such reactions.

However, the authors did not find cells for x-ray studies in the known state of the art, the design of which provides for the possibility of studying liquid samples while maintaining a relatively high temperature of the test sample of more than 100 °C and creating a pressure of more than 2 bar over the reaction mixture by supplying a gas flow.

The cell for X-ray spectral diagnostics of liquid-phase samples contains a hollow body, the upper surface of which is provided with a protrusion, in which a glass with a test sample made of a polymeric X-ray transparent material is installed, equipped with a rim in the upper part, the outer diameter of which is equal to the outer diameter of the protrusion, a housing cover rigidly connected to the housing and made with holes for installing pipes for gas supply, a hole is made on the side surface of the housing, into which a window is installed, made of a radiolucent material and tightly adjacent to the wall of the glass, a fixing element with a central hole, located over the window and rigidly connected to the side wall of the housing, heating elements located in the channels of the housing, a temperature sensor located in the opening of the housing.

The body and the ledge can be cylindrical, oval or rectangular.

The hole in the side wall of the housing and the window can be made in the form of a truncated cone, the smaller base of which is located on the side of the glass.

A gasket made of a chemically and heat-resistant sealing material, such as PTFE or perfluorinated rubber, can be installed in the opening of the side wall of the housing.

A spacer can be installed between the fixing element and the window, made of a heat-resistant material with a central hole, the diameter of which is equal to the diameter of the central hole of the fixing element.

The central hole in the fixing element and in the spacer can be oval or rectangular.

The invention is illustrated in the drawing.

Fig. 1. Cell for X-ray spectral diagnostics of liquid-phase samples in a controlled atmosphere at high pressures and temperatures in the operando mode

The cell for X-ray spectral diagnostics of liquid-phase samples contains a hollow body (1) made of durable corrosion-resistant metal or alloy (for example, stainless steel). The body (1) of the cell can be cylindrical, oval or rectangular. The upper part of the body (1) is provided with a cylindrical protrusion (2), in which a thin-walled cup (3) is installed made of a polymeric X-ray transparent material with high temperature and chemical resistance (for example, fluoroplast), so that the walls of the cup fit snugly against the walls of the body. The glass (3) in the upper part is provided with a protruding rim, the outer diameter of which is equal to the outer diameter of the protrusion (2) of the body (1). Due to the protruding side of the glass (3), the position of the glass inside the body (1) is fixed. From above, the body (1) is closed with a lid (4) made of the same material as the body (1). For reliable fastening to the body, the cover can be screwed to the body, or it can be screwed to the body using a flange. Holes (5) are made in the cover (4) for installing pipes for supplying gas to the internal cavity of the cup (3). For tight connection of tubes with cover (4), appropriate adapters can be used for connecting tubes for supplying gaseous atmosphere and connecting manometric control devices. Adapters can be connected to the cover (4) using a threaded connection, using a welded connection, or made integral with the cover (4). The sealing of the inner volume of the cup (3) when installing the lid (4) is provided by the protruding rim, the outer diameter of which is equal to the outer diameter of the protrusion (2), which ensures a snug fit of the rim to the upper surface of the walls of the protrusion (2). Additionally, a gasket can be installed, made commensurate with the protruding rim of the cup (3). The gasket must be made of a chemically and heat resistant sealing material such as perfluorinated rubber. A central hole (6) is made on the side surface of the housing (1). The cross section of the hole (6) can be truncated-conical (to increase strength and better resist pressure inside the cell). A window (7) is installed in the hole (6) on the side surface of the body (1), made of a durable radiolucent material, for example, glassy carbon or beryllium. The shape of the window (7) coincides with the shape of the cross section of the hole (6).

To ensure greater tightness of the internal volume of the housing, a gasket (8) made of a chemically and heat-resistant sealing material, for example, fluoroplast or perfluorinated rubber, can be installed in the hole (6) of the side wall of the housing (1). The shape of the gasket (8) must match the shape of the hole (6), for example an annular or a truncated cone. The thickness of the gasket (8) is equal to the wall thickness of the housing (1). The window (7) is placed in the hole (6) of the side wall of the housing (1) after the gasket (8) is installed. The window (7) is installed in the body (1) in such a way that inside the body it closely adjoins the outer wall of the cup (3) to prevent its deformation under the action of internal pressure. A fixing element (9) with a central hole is installed over the window (7). With the help of the fixing element (9), a rigid connection and tight fit of the window (7) to the side surface of the housing (1) is ensured. The fixing element (9) can be made in the form of a plate made of the body material. The locking element (9) can be connected to the side wall of the housing using a flange and/or screws (10). The fixing element (9) can be additionally connected to the housing using a bracket or clamp. The central hole in the fixing element (9) allows the passage of X-rays. The hole in the fixing element (9) is preferably made of the maximum size while maintaining the necessary strength, rigidity and reliable pressing of the window (7). To increase the fluorescence exit angle, the hole can be expanded from the outside. A spacer (11) can be installed between the fixing element (9) and the window (7) to ensure uniform pressure from the side of the fixing element (9) on the window (7). Preferably, the spacer (11) is made of a solid, temperature-resistant polymer, such as PTFE. The spacer (11) is made with a central hole for the passage of x-ray radiation, which coincides in shape with the hole in the fixing element (9).

Holes with channels are made in the upper and lower parts of the body (1), into which heating elements (12) are installed. Cartridge heaters, which are connected to a suitable voltage source or temperature controller, can be used as heating elements. The heating elements (12) can be fixed in the casing with set screws. The temperature sensor (13) can have an arbitrary location, for example, in the hole in the upper part of the side wall of the housing (1). It is preferable to install a temperature sensor (13) near the glass (3) to obtain more reliable data and the possibility of more accurate control of the temperature of the reactions taking place.

The heating elements (12) and the temperature sensor (13) are connected to devices for controlling and maintaining the temperature, for example, to a thermostat or a proportional-integral-derivative (PID) controller.

The cell can be made of a durable corrosion-resistant metal or alloy, such as stainless steel.

The cell works as follows.

The investigated liquid sample, for example, a homogeneous catalyst, is placed in a beaker (3). The glass (3) is installed in the protrusion (2) of the body (1), then the lid (4) is closed from above. The cell is placed in an experimental setup for conducting X-ray absorption spectroscopy experiments, for example, in the experimental station of the synchrotron. With the help of heating elements (12) the test sample in the glass (3) is heated to the required temperature by applying current. Control over the temperature of the test sample is carried out using a temperature sensor (13). Through the tubes installed in the holes (5) of the cover (4) of the housing, the required atmosphere is created in the cell by supplying a gas flow under a certain pressure. Install the cell in a laboratory spectrometer. X-ray radiation, passing through the window (7) in the housing and the wall of the glass (3), interacts with the test sample, causing the effect of X-ray fluorescence. The fluorescence radiation, propagating in all directions, including penetrating through the wall of the glass (3) and the window (7) in the body to the outside of the cell, where it is recorded by an X-ray detector. In this way, X-ray absorption spectra are measured in controlled inert or reactive media.

By analyzing the obtained X-ray absorption spectra using the proposed cell design, it is possible to track in real time the dynamics of the local atomic and electronic structure of the sample under study in the cell, which in turn allows obtaining information about the chemical processes occurring in the sample under study. The results of studying the obtained spectra can be used to improve the structure and methods of synthesis, for example, of homogeneous catalysts in order to increase the yield of catalytic reaction products or slow down catalyst degradation.

The novelty of the device lies in the fact that in the body of the cell, which in principle has the capabilities of a chemical reactor-autoclave, there is a window for the passage of X-rays to the reaction mixture. This makes it possible not only to carry out chemical reactions with liquid samples and mixtures that occur at high pressure and temperature, as in a conventional chemical reactor, but also to diagnose these chemical reactions in real time using X-ray absorption spectroscopy, tracking changes in the local atomic and electronic structure of liquid samples. and the formation of new substances during the reaction.

The high tightness of the cell, achieved by tightly clamping the protruding rim of the glass between the lid and the protrusion made on the upper surface of the body, makes it possible to create and control the required values of the technological modes of the reactions occurring in the sample. In addition, the conical shape of the hole in the side wall of the housing and the X-ray transparent window make it possible to increase the available solid angle for the exit of X-ray fluorescence, while at the same time not reducing the strength of the housing and window excessively and, as a result, the allowable working pressure.

Thanks to the possibility of X-ray spectral diagnostics of chemical processes in the operando mode, it becomes possible to obtain the most reliable data on chemical processes occurring in the system under study, including various short-lived intermediate phases. These data can be used to improve the studied liquid-phase chemical system.

The ability to maintain a high temperature and pressure over the studied reaction mixture, created by a gaseous atmosphere, expands the applicability of this cell for complex cases of hydrothermal and solvothermal synthesis and homogeneous catalysis.

An example of the practical application of the proposed cell can serve as an experiment carried out on the basis of the SOLEIL synchrotron center (Saint-Aubin, France). Within the framework of this experiment, samples of homogeneous catalysts based on ruthenium molecular complexes were studied in the course of the catalytic hydrogenation of acetone. A mixture of 0.01 mmol RuBr3, 1.7 mmol Bu4PBr, and 0.5 mmol acetone was placed into the cell. An atmosphere of carbon monoxide and hydrogen was created above the mixture at a partial pressure of 5 bar and 35 bar, respectively. The cell was heated from ambient temperature (22°C) to 180°C. During heating, the X-ray absorption spectra beyond the K-edge of ruthenium were measured in the operando mode. A change in the spectrum profile was recorded in real time, indicating a change in the catalytic activity of ruthenium in the system as the temperature increased. The obtained data are presented in the figure.

Claims (6)

1. A cell for X-ray spectral diagnostics of liquid-phase samples, containing a hollow body, the upper surface of which is provided with a ledge, in which a glass with a test sample made of a polymeric X-ray transparent material is installed, equipped with a rim in the upper part, the outer diameter of which is equal to the outer diameter of the ledge, a cover rigidly connected to body and made with holes for installing tubes for gas supply, on the side surface of the body there is a hole in which a window is installed, made of radiolucent material and tightly adjacent to the glass wall, a fixing element with a central hole located over the window and rigidly connected to the side wall housing, heating elements located in the channels of the housing, temperature sensor located in the opening of the housing. 2. The cell according to claim 1, in which the body and the protrusion are cylindrical, oval or rectangular. 3. The cell according to claim 1, in which the hole in the side wall of the housing and the window are made in the form of a truncated cone, the smaller base of which is located on the side of the glass. 4. The cell according to claim 1, in which a gasket made of a chemically and heat-resistant sealing material, such as fluoroplast or perfluorinated rubber, is installed in the opening of the side wall of the housing. 5. The cell according to claim 1, in which a spacer is installed between the fixing element and the window, made of a heat-resistant material with a central hole, the diameter of which is equal to the diameter of the central hole of the fixing element. 6. The cell according to claim 5, in which the central hole in the fixing element and in the spacer is made of an oval or rectangular shape.

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