Headspace sampler and its use for monitoring chemical reactions

Abstract

Headspace sampler and its use for monitoring chemical reactions. This application relates to a headspace sampler adapted for operando monitoring of chemical reactions. It also relates to the use of the headspace sampler according to the invention for monitoring a chemical reaction and / or for filling a container with a precise, predefined quantity of material.

Description

Title of the invention: Headspace sampler and its use for monitoring chemical reactions technical field

[0001] The present invention relates to the technical field of instruments for detecting and monitoring chemical reactions. It relates in particular to a headspace sampler that enables the monitoring of chemical reactions by operando sampling. Technological background

[0002] Headspace samplers are analytical instruments classically used, in association with a gas chromatography apparatus, to analyze the content of predefined volatile compounds of a sample, most often a sample of a liquid or solid condensed phase.

[0003] The conventional method involves placing the sample, most often in the form of a liquid or solid condensed phase, in a pillbox or other suitable container. Headspace sampling can be likened to vapor-phase extraction of all or part of the volatile components of the sample that have diffused into the gaseous phase of the headspace. The headspace sampler includes a sample gas collection channel connected to a needle. This needle is introduced into the sample's headspace in the pillbox after equilibration, and by pressurizing the pillbox, the gaseous phase of the sample's headspace is collected. The collected sample then passes through a sampling loop and is subsequently directed to the inlet of a gas chromatography instrument, optionally coupled to a mass spectrometer.

[0004] While this type of operation is suitable for analyzing samples at equilibrium, it does not allow for monitoring changes in the headspace composition of a sample that is not at equilibrium. This is because sampling must be carried out using specific containers or pillboxes and cannot be performed in just any container. Furthermore, the use of the needle does not allow for maintaining an airtight seal of the container after sampling. Therefore, it is not possible to take samples repeatedly from the same container.

[0005] Furthermore, the determination of the quantities of each volatile species analyzed is carried out by comparison with calibration curves previously established for the appropriate container volume. These calibration curves are not suitable if the container volume is different. Moreover, these calibration curves cannot be established (or are extremely difficult to establish) when the species being analyzed is a gas and not a volatile compound in equilibrium between a liquid sample and the headspace.

[0006] It would therefore be useful to have a headspace sampler that would allow for repeated sampling from the same container, in order to monitor the composition of the headspace over time, particularly during a chemical reaction. Advantageously, this headspace sampler should also allow for the creation of calibration curves adapted to any container and any volatile species analyzed.

[0007] In this context, the Inventors have surprisingly demonstrated that it is possible to modify a conventional headspace sampler to allow for repeated sampling from the same container, thus enabling monitoring of the headspace composition of a container. Another advantage of the headspace sampler according to the invention is that it also allows sampling at atmospheric pressure, without the need to pressurize the reactor. Summary of the invention

[0008] Thus, a first object of the present invention is a headspace sampler, comprising: a. A reactor suitable for carrying out a chemical reaction, b. A gas introduction channel comprising at least one flow controller of gas, c. A sampling loop adapted to be connected to an input of a gas-phase chromatograph, d. An output channel for the sampling loop allowing the sampling loop and transfer line to be placed at a desired pressure, in particular under vacuum or atmospheric pressure, e. A reactor outlet channel, f. An inlet valve (2) located between the reactor and the gas inlet channel, g. A purge valve (3) located between the reactor and the reactor outlet channel, h. A sampling valve (4) located between the reactor and the sampling loop, i. An outlet valve (5), j. A loop valve (1) located after the sampling loop, and k. A controller that can act on at least one gas flow controller and / or on at least one valve of the sampler.

[0009] In one embodiment, the headspace sampler according to the invention it also includes a pressure detector within the reactor, said pressure detector being connected to the sampler controller.

[0010] In one embodiment, the headspace sampler according to the invention further includes an outlet valve for connecting the outlet channel of the sampling loop to a high vacuum inlet and / or an atmospheric pressure outlet.

[0011] In one embodiment, the gas introduction channel comprises at least two introduction channels for two gases, preferably two different gases, each gas introduction channel being associated with a flow controller for said gas connected to the sampler controller.

[0012] In one embodiment, the actuation of at least one of the valves, preferably the actuation of all the valves, is automated.

[0013] In one embodiment, the reactor is an electrolysis cell.

[0014] A second object of the invention is the use of a headspace sampler according to the invention for monitoring a chemical reaction, including sampling the headspace of the reactor in which a chemical reaction is carried out at several times during the reaction.

[0015] In one embodiment, the chemical reaction implemented in the reactor is a reaction producing at least one permanent gas such as dihydrogen, carbon monoxide, ethane and methane.

[0016] In one embodiment, the chemical reaction is chosen from the group consisting of a photochemical reaction, a dihydrogen production reaction, and an electroreduction of carbon dioxide.

[0017] A third object of the invention is the use of a headspace sampler according to the invention for filling a container such as an NMR tube with a predetermined volume or a predetermined amount of a gas or a mixture of gases. Brief description of the drawings

[0018] Fig. 1 is a schematic of a headspace sampler according to the invention, and illustrates its operation for monitoring an electrolysis reaction.

[0019] Fig. 2 is a diagram of a headspace sampler according to the invention when used in a configuration allowing the injection of a precise quantity of a precise species into a container. Detailed description

[0020] A first object of the invention is a headspace sampler comprising a number of elements.

[0021] Definitions

[0022] A "permanent gas" is a gas that cannot liquefy simply by increasing the pressure at ambient temperature; in other words, a gas whose critical temperature is lower than the ambient temperature. Ambient temperature is defined as a temperature between 15°C and 25°C. Examples of permanent gases include He, H₂, Ne, N₂, Ar, O₂, Kr, CO, CH₄, NO, and air.

[0023] According to the present invention, the term "operand," associated with sampling, refers to the fact that sampling is carried out directly in the reactor in which the chemical reaction is performed. This type of sampling does not require transferring the sample taken into a pillbox or other container specially adapted for the sampler.

[0024] Each of the valves of the headspace sampler according to the invention can take several positions. In the present invention, the terms "open" and "closed", as well as other terms of the same family, refer interchangeably to two different positions of the same valve, without the "open" position necessarily being a position in which a gas flow passes or the "closed" position necessarily being a position in which no gas flow passes.

[0025] The term “vacuum” or “high vacuum” refers to a pressure generally less than about 1 mbar, in particular a pressure between 103 and 101 mbars.

[0026] The terms "before" and "after", when they indicate relative positions of two elements of the headspace sampler according to the invention, refer to the order in which the gas flow passes through said elements when the sampler is in operation.

[0027] The term "approximately" is used in the present invention to designate an approximation. When used with reference to a numerical value, it modifies that numerical value by extending it 10% above and 10% below said numerical value, preferably 5% above and 5% below said numerical value, in particular 1% above and 1% below said numerical value.

[0028] Reactor

[0029] The reactor can be made of any material, in any shape and any size. The reactor is a hermetic reactor. In one embodiment, the reactor is a glass reactor.

[0030] In some embodiments, the reactor is an electrolysis cell. An electrolysis cell is a reactor in which two electrodes are immersed, allowing a current to pass through the reaction medium present in the electrolysis cell.

[0031] In some embodiments, the reactor includes a pressure sensor within the reactor, such as a pressure gauge. This pressure sensor is advantageously- securely connected to the controller.

[0032] Gas introduction channel.

[0033] The gas introduction channel connects one or more gas sources to the reactor inlet valve. In one embodiment, a gas flow controller is associated with each gas source on the gas introduction channel. The gas introduction channel may include a branch for each gas source. The gas sources may be any suitable source, including pressurized gas cylinders. The gases that may be introduced can vary widely. For example, the gas sources may be cylinders of N2, CO2, or a gas mixture, including a standard gas mixture for producing calibration curves.

[0034] In particular embodiments, the gas introduction channel comprises one gas source associated with a gas flow controller, two gas sources each associated with a gas flow controller, three gas sources each associated with a gas flow controller, four gas sources each associated with a gas flow controller, five gas sources each associated with a gas flow controller, or as many gas sources and associated flow controllers as necessary depending on the number of gas types required.

[0035] In the case where the headspace sampler includes several gas flow controllers at the system inlet, the gas introduction channel allows the introduction into the reactor of the gas mixture whose quantity is defined respectively by each of the gas flow controllers.

[0036] In certain embodiments, the gas introduction channel is connected to a separate container. Implementing the sampler in this configuration allows the injection of a precise quantity of a volatile species, in particular a permanent gas, into this container. This can, for example, allow the filling of NMR (nuclear magnetic resonance) tubes with an exact volume of a gas.

[0037] Sampling loop

[0038] The sampling loop is located between the sampling valve at the reactor outlet and the outlet channel of the sampling loop.

[0039] The sampling loop is adapted to be connected to an input of a gas chromatograph. The sampling loop can also be considered as part of the gas chromatograph.

[0040] The sampling loop contains a fixed volume of sample taken from the reactor headspace, in particular for repeated injections into the gas chromatography injection port.

[0041] The sampling loop may, in certain embodiments, include heating means suitable for heating the sample that is present and / or circulating in the sampling loop. The sampling loop of the headspace sampling according to the invention is similar to a sampling loop present in a conventional headspace sampling.

[0042] The volume of gas that passes from the reactor to the sampling loop can be any volume adapted according in particular to the volume of the reactor and the expected quantity of the species to be quantified.

[0043] In some embodiments, the volume of gas taken during sampling is between 1 microlitre and 10 millilitres, preferably between 20 microlitres and 2 millilitres.

[0044] In some embodiments, the sampler includes several sampling loops, in particular as many sampling loops as there are analysis channels on the gas chromatograph.

[0045] Sampling loop output channel

[0046] The sampling loop output channel allows the sampling loop and the transfer line to be placed at a desired pressure, in particular under vacuum or atmospheric pressure.

[0047] In some embodiments, the output channel of the sampling loop includes a GC sampling valve, which can be automated.

[0048] Another object of the invention is a device comprising a headspace sampler according to the invention, a gas chromatograph comprising one or more analysis channels, and optionally different detectors (in particular TCD, FID, mass spectrograph), the gas chromatograph being connected to the sampling loop of the headspace sampler.

[0049] The sampling loop outlet channel is located after the sampling loop. A loop valve and / or an outlet valve may be present on this sampling loop outlet channel. Depending on the positioning of the outlet valve, this channel can be connected either to a high vacuum port (typically less than 1 mbar) or to a device outlet.

[0050] Reactor outlet channel

[0051] The reactor outlet channel is located after the reactor and is connected to the reactor when the sampling valve is in a position that does not allow the reactor to be isolated. A purge valve may be present before this reactor outlet channel.

[0052] Inlet valve

[0053] The inlet valve is located between the gas inlet channel and the reactor. Opening it allows gas to be introduced into the reactor. Closing it helps to seal the reactor. In some embodiments, several inlet valves, associated with several gas inlet channels into the reactor, are present.

[0054] Bear valve

[0055] The purge valve is located before the reactor outlet channel and can be opened in particular to adjust the pressure within the reactor, and / or to evacuate purge gases during system purges.

[0056] Sampling valve

[0057] The sampling valve is located on the reactor outlet channel, and allows in particular the reactor to be isolated hermetically and the gas from the reactor headspace to be directed to the sampling loop.

[0058] Loop valve

[0059] The loop valve is located on the outlet channel of the sampling loop. It isolates the sample transfer line (including the sampling loop) from the vacuum source. It is therefore kept open to maintain the entire line under dynamic vacuum. It is closed during sampling to maintain a static vacuum on the transfer line before the sampling valve is opened.

[0060] Outlet valve

[0061] The outlet valve is located on the outlet channel of the sampling loop, after the loop valve. This valve allows the outlet channel of the sampling loop to be connected either to a high vacuum port or to an outlet, in particular an atmospheric pressure outlet.

[0062] Controller

[0063] The controller may include a graphical user interface, for example a liquid crystal display (LCD) through which the values ​​of the control parameters can be set, for example through a menu such as a graphical menu.

[0064] In certain embodiments, the headspace sampler according to the invention is automated, i.e., the controller can be programmed so that at least one of the necessary valve switching and / or gas flow adjustment actions does not require user intervention at the time of that action. Preferably, the headspace sampler according to the invention is fully automated, i.e., all the necessary valve switching and / or gas flow adjustment actions are performed during operation without any user intervention being required.

[0065] Thus, the controller may be able to perform all or part of the following operations: calculations, recording of process parameters, modification of process parameters, reading of pressure, volume and / or temperature values, and control of the change of state of valves.

[0066] The controller may be based on a programmable microcontroller board such as those marketed by the Arduino company, in particular the Arduino Mega board. The microcontroller board can be programmed using a dedicated integrated development environment, such as the C++ programming language. The controller's hardware components can be integrated via a custom-designed printed circuit board (PCB) tailored to the physical requirements of the controller and / or the graphical interface.

[0067] Headspace composition tracking

[0068] The headspace sampler according to the present invention is particularly well-suited for monitoring the composition of the headspace of a container, referred to herein as a reactor, over time. This is particularly useful for monitoring the evolution and / or progress of a chemical reaction taking place within the reactor. Operando headspace sampling is therefore implemented.

[0069] Thus, another object of the invention is the use of a headspace sampler according to the invention for monitoring a chemical reaction, comprising sampling the headspace of the reactor in which a chemical reaction is carried out at several points during the reaction. The sampling is generally followed by the quantification, preferably by gas chromatography, of one or more volatile and / or gaseous species identified beforehand.

[0070] Quantification may include comparing a chromatogram of the volatile species or the target gas obtained by the headspace sampler according to the invention coupled to a gas chromatograph, with a calibration curve of said volatile species or said gas carried out under the same conditions.

[0071] Sampling is preferably carried out several times during the reaction. A person skilled in the art can determine the number of samples, the duration of the sampling, and / or the sampling frequency based on various parameters such as the size of the reactor, the nature of the chemical reaction being monitored, and / or the nature of the species whose quantity is being analyzed.

[0072] Sampling can be carried out at a fixed frequency throughout the reaction. Conversely, the sampling frequency can be adjusted during the monitoring of the reaction, particularly based on the results of the quantification of previous sampling.

[0073] In one embodiment, after each sampling during the monitoring of the chemical reaction, a volume of gas equivalent to that which was sampled from the reactor during the sampling is introduced into the reactor. This makes it possible, in particular, to maintain the conditions necessary for the continuation of the chemical reaction in the reactor, notably the pressure in the reactor. The quantity of gas to be introduced can be determined by means of the pressure sensor present within the reactor. In such an embodiment, said pressure sensor is preferably connected to the controller, and the controller is adapted to open the reactor inlet valve and / or trigger a suitable gas flow into the gas introduction channel.

[0074] The species quantified at each sampling step are volatile species and / or gases. In some embodiments, these are gases, particularly permanent gases. The nature of the volatile species and / or gases quantified at each sampling step naturally depends on the nature of the reaction carried out in the reactor. The volatile species and / or gases quantified at each sampling step may, for example, be reactants, products, and / or intermediate products of the reaction carried out in the reactor.

[0075] In some embodiments, only one species is quantified at each sampling. In other embodiments, several species are quantified at each sampling.

[0076] Examples of gases that can be quantified include, in particular, dihydrogen, carbon dioxide, carbon monoxide, ethane and methylene.

[0077] Examples of chemical reactions that can be monitored with the headspace sampler according to the invention include, in particular, photochemical reactions, CO2 electroreduction reactions, dihydrogen production reactions, and more generally any reaction leading to the production of at least one permanent gas.

[0078] In certain embodiments, the chemical reaction being monitored is a reaction that occurs during the charging or discharging of a battery. In this case, the use of the headspace sampler according to the invention can, in particular, make it possible to monitor the battery's degradation state. The quantity of gases detected can indeed be correlated with the battery's degradation state.

[0079] Calibration

[0080] The headspace sampler according to the invention can be used to generate one or more calibration curves for the species whose quantity is being analyzed. These curves will depend, in particular, on the reactor used. Preferably, the establishment of these calibration curves is carried out before the reaction is initiated in the reactor of the headspace sampler according to the invention. They can also be established from the reaction medium after the reaction, provided that a preliminary purging is performed.

[0081] Operating modes

[0082] The headspace sampler according to the present invention can be used in different operating modes. Among the different modes, the following may be mentioned: a. The static mode, which allows a purge sequence and quantification experiments to be carried out in a closed reactor. Sampling is performed at defined intervals.

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[0089]

[0090] b. The flow mode, which allows for the implementation of a purge sequence and quantification experiments under a continuous flow of carrier gas. Sampling is carried out continuously at defined intervals by changing the position of the GC sampling valve. c. Volume mode, which allows a precise quantity (in moles) or volume of gas to be injected into any container, keeping that container hermetically sealed after injection. d. The NMR (nuclear magnetic resonance) mode, which allows the injection of a precise quantity (in moles) or volume of gas into any container, particularly an NMR tube. In some embodiments, the container is placed at a reduced pressure via a selector valve before gas injection. e. The calibration mode, which allows the injection of a precise quantity of a standard gas mixture into a reactor and the acquisition of a GC chromatogram. This mode may include successive injections / samples, in particular from 2 to 10, notably 4, successive injections / samples. Reactor purges may be introduced between two consecutive injections / samples. The invention will be better understood by reading the following examples, which are presented by way of illustration and not limitation of the invention. Examples Example 1: Sampler according to the invention and sampling principle Fig. 1 is a schematic of a headspace sampler according to the invention, and illustrates its configuration for monitoring an electrolysis reaction. Each sampling with the sampler in [Fig.1] is carried out as follows: has. Pressure equalization: The reactor pressure is adjusted to a sampling pressure value 30 seconds before sampling. This adjustment is implemented via the inlet valve (2), using the desired gas. A gas flow rate is set by the controller on one of the flow controllers for a duration sufficient to purge the inlet line. The position of the inlet valve (2) is then adjusted to allow gas to enter the reactor until the reactor pressure, measured by the pressure gauge, equals the sampling pressure value. The position of the inlet valve (2) is then adjusted again, isolating the reactor. b. Sample transfer: The reactor is left to equilibrate to the sampling pressure for a period of time. A fixed duration, typically on the order of 4 to 10 seconds, is set. During this time, the loop valve (1) is closed to isolate the transfer line from the vacuum source. Once the equilibration time has elapsed, the position of the sampling valve (4) is changed, thus connecting the transfer line to the reactor headspace. Pressure equilibration then leads to the transfer of the sample from the headspace to the sampling loop.

[0091] c. Injection into the gas chromatography (GC) apparatus:

[0092] After 4 seconds, the GC sampling valve is turned, the gaseous content from the sampling loop is thus injected into the input port of the gas chromatography instrument.

[0093] Example 2: Production of calibration curves with a sampler according to the invention

[0094] The sampler in [Fig. 1] can be used to produce calibration curves as detailed below from external standards under conditions identical to those used during the reaction. Thus, the headspace sampler according to the invention allows known quantities of standard gas to be injected into the reactor headspace using the corresponding standard gas mixtures. The calibration curves are produced from a mixture of standard gases as follows:

[0095] a. Removal of gas from the headspace:

[0096] The diaphragm pump is activated and the purge valve (3) is opened until the pressure within the reactor decreases to a predetermined value. The predetermined value is determined based on the volume of standard gas mixture to be added, so that when the standard gas mixture is added, the final pressure within the reactor remains below atmospheric pressure.

[0097] b. Addition of the standard gas mixture:

[0098] The controller sets a flow rate on one flow controller or on both controllers gas flow is introduced simultaneously for a sufficient time to purge the gas inlet channel with the standard gas mixture. The position of the inlet valve (2) is then changed to allow the standard gas mixture to enter the reactor until the volume counted by the controller equals the predetermined volume corresponding to the molar quantity of standard gas mixture to be added, then the inlet valve (2) returns to the closed position.

[0099] c. Pressure equalization:

[0100] The reactor pressure is balanced to a predetermined pressure value identical to the sampling pressure used for subsequent quantification experiments, a few seconds before sampling via the inlet valve (2), with any gas (determined by the user).

[0101] d. Sample transfer:

[0102] The reactor is left to equilibrate at the sampling pressure for a few seconds. The loop valve (1) is closed to isolate the transfer line between the reactor and the sampling loop from the vacuum source. Once equilibrium is reached, the sampling valve (4) is opened, connecting the transfer line to the reactor headspace. The pressure will rapidly equalize in both compartments.

[0103] e. GC injection:

[0104] After 4 seconds, the GC sampling valve is switched on, allowing the gaseous contents of the sampling loop to be injected into the GC injection port. The resulting chromatogram contains peaks corresponding to the compounds present in the standard gas mixture. The area of ​​each peak is correlated with the concentration of standard injected into the reactor in step b. This correlation constitutes a point (or level) on the calibration curve. By repeating the operation, incrementally increasing the amount of standard injected, a calibration curve can be established over a desired concentration range.

Claims

Demands

1. Headspace sample, comprising: a. A reactor suitable for carrying out a chemical reaction, b. A gas introduction channel comprising at least one gas flow controller, c. A sampling loop adapted to be connected to an input of a gas chromatograph, d. An output channel for the sampling loop allowing the sampling loop and transfer line to be placed at a desired pressure, in particular under vacuum or atmospheric pressure, e. A reactor outlet channel, f. An inlet valve (2) located between the reactor and the gas inlet channel, g. A purge valve (3) located between the reactor and the reactor outlet channel, h. A sampling valve (4) located between the reactor and the sampling loop, i. A loop valve (1) located after the sampling loop, and j. A controller that can act on at least one gas flow controller and / or on at least one valve of the sampler.

2. Headspace sampler according to claim 1, further comprising a pressure detector within the reactor, said pressure detector being connected to the sampler controller.

3. Headspace sampler according to claim 1 or claim 2, further comprising an outlet valve for connecting the outlet channel of the sampling loop to a high vacuum inlet and / or to an atmospheric pressure outlet.

4. Headspace sampler according to any one of claims 1 to 3, wherein the gas introduction channel comprises at least two introduction channels for two gases, preferably two different gases, each gas introduction channel being associated with a flow controller of said gas connected to the sample controller.

5. Headspace sampler according to any one of claims 1 to 4, wherein the actuation of at least one of the valves, preferably the actuation of all the valves, is automated.

6. Headspace sampler according to any one of claims 1 to 5, wherein the reactor is an electrolysis cell.

7. Use of a headspace sampler according to any one of claims 1 to 6 for monitoring a chemical reaction, including sampling the headspace of the reactor in which a chemical reaction is carried out at several times during the reaction.

8. Use according to claim 7, wherein the chemical reaction carried out in the reactor is a reaction producing at least one permanent gas such as dihydrogen, carbon monoxide, ethane and methane.

9. Use according to claim 7 or 8, wherein the chemical reaction is selected from the group consisting of a photochemical reaction, a dihydrogen production reaction, and an electroreduction of carbon dioxide.

10. Use of a headspace sampler according to any one of claims 1 to 6 for filling a container such as an NMR tube with a predetermined volume or predetermined amount of a gas or gas mixture.

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