Headspace sampler and its use for monitoring chemical reactions

Abstract

Headspace sampler and its use for monitoring chemical reactions The present application relates to a headspace sampler suitable for the 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 predefined precise 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 which allows the monitoring of chemical reactions by operando sampling. Technological background

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

[0003] The conventional operation consists of 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 a vapor phase extraction of all or part of the volatile components of the sample which have diffused into the gas phase of the headspace. The headspace sampler comprises a sample gas collection channel which is connected to a needle. This needle is introduced into the headspace of the sample in the pillbox after equilibration and, by pressurizing the pillbox, gas phase from the headspace of the sample is collected. The collected sample then passes through a sampling loop and is then directed to the inlet of a gas chromatography apparatus, possibly coupled to a mass spectrometry apparatus.

[0004] This type of operation, although suitable for analyzing samples at equilibrium, does not, however, allow the evolution of the composition of the headspace of a sample that is not at equilibrium to be monitored. Indeed, the sample must be taken from specific containers or pillboxes, and cannot be taken from any container. Furthermore, the use of the needle does not allow the container to be kept hermetically sealed after sampling. It is therefore not possible to take samples several times from the same container.

[0005] Furthermore, the determination of the quantities of each volatile species analyzed is carried out by comparison with calibration curves produced upstream for the appropriate container volume. These calibration curves are not suitable if the container volume is different. Furthermore, these calibration curves cannot be produced (or only with great difficulty) in the case where the species that one seeks to analyze 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 samples to be taken several times from the same container, in order to allow the composition of the headspace to be monitored over time, in particular during a chemical reaction. Advantageously, this headspace sampler should also allow calibration curves to be produced that are suitable regardless of the container, and regardless of the volatile species analyzed.

[0007] In this context, the inventors have surprisingly demonstrated that it is possible to modify a conventional headspace sampler to allow samples to be taken several times from the same container, thus allowing the composition of the headspace of a container to be monitored. Another advantage of the head 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 suitable for connection to an input of a gas chromatograph, d. A sample loop outlet channel allowing the sample loop and transfer line to be placed at a desired pressure, such as vacuum or atmospheric pressure, e. A reactor outlet channel, f. An inlet valve (2) located between the reactor and the gas introduction 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 for acting on at least one gas flow controller and / or at least one valve of the sampler.

[0009] In one embodiment, the headspace sampler according to the invention further comprises a detector of the pressure within the reactor, said pressure detector being connected to the sampler controller.

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

[0011] In one embodiment, the gas introduction channel comprises at least two channels for introducing 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, comprising 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 carried out 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 selected from the group consisting of a photochemistry reaction, a hydrogen 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 quantity of material of a gas or a mixture of gases. Brief description of the drawings

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

[0019] [Fig.2] is a schematic 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 pressure at room temperature, in other words a gas whose critical temperature is lower than room temperature. Room temperature means a temperature between 15°C and 25°C. Examples of permanent gases include He, H 2, 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 the sampling is carried out directly in the reactor in which the chemical reaction is carried out. This type of sampling does not require the transfer of the sample taken into a pillbox or other container specially adapted to 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 families, refer indifferently 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 approximately 1 mbar, in particular a pressure between 103 and 10 1 mbar.

[0026] The terms "before" and "after", when indicating 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 "about" is used herein to denote an approximation. When used in 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, particularly 1% above and 1% below said numerical value.

[0028] Reactor

[0029] The reactor may be of any material, shape, or size. The reactor is a sealed reactor. In one embodiment, the reactor is a glass reactor.

[0030] In certain 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 comprises a sensor for the pressure within the reactor, such as a pressure gauge. This pressure sensor is advantageously carefully 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 comprise a branch per gas source. The gas sources may independently be any suitable source, including pressurized gas cylinders. The gases that may be introduced may vary widely. For example, the gas sources may be cylinders of N2, CO2, or a mixture of gases, 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 types of gas required.

[0035] In the case where the headspace sampler comprises several gas flow controllers at the inlet of the system, the gas introduction channel makes it possible to introduce into the reactor the mixture of gases, the quantity of which is defined respectively by each of the gas flow controllers.

[0036] In some embodiments, the gas introduction channel is connected to a different container. An implementation of 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 allow, for example, 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 sampling loop outlet channel.

[0039] The sampling loop is adapted to be connected to an inlet 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, particularly for repeated injections into the gas chromatography injection port.

[0041] The sampling loop may comprise in certain embodiments heating means adapted to heat the sample which is present and / or circulates in the sampling loop. The sampling loop of the headspace sampler according to the invention is similar to a sampling loop present in a conventional headspace sampler.

[0042] The volume of gas which passes from the reactor to the sampling loop can be any suitable volume depending in particular on the volume of the reactor and the expected quantity of the species to be quantified.

[0043] In some embodiments, the volume of gas collected during sampling is between 1 microliter and 10 milliliters, preferably between 20 microliters and 2 milliliters.

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

[0045] Sample Loop Output Channel

[0046] The sampling loop outlet channel allows the sampling loop and transfer line to be placed at a desired pressure, such as vacuum or atmospheric pressure.

[0047] In some embodiments, the output channel of the sampling loop comprises a GC sampling valve, which may 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 possibly different detectors (in particular TCD, FID, mass spectrograph), the gas chromatograph being connected to the sampling loop of the headspace sampler.

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

[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 introduction channel and the reactor. Its opening allows gas to be introduced into the reactor. Its closing helps to make the reactor airtight. In certain embodiments, several inlet valves, associated with several gas introduction channels into the reactor, are present.

[0054] Bear valve

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

[0056] Sampling valve

[0057] The sampling valve is located on the outlet channel of the reactor, and in particular makes it possible to isolate the reactor hermetically and to direct the gas coming from the head space of the reactor towards 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 so as to maintain the entire line under dynamic vacuum. It is closed at the time of sampling so as 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 makes it possible in particular to connect the outlet channel of the sampling loop either to a high vacuum port or to an outlet, in particular an outlet at atmospheric pressure.

[0062] Controller

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

[0064] In some 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 action at the time of that action. Preferably, the headspace sampler according to the invention is fully automated, i.e., all necessary valve switching and / or gas flow adjustment actions are performed during operation without any user action 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 card such as those marketed by the company Arduino, in particular the Arduino Mega card. 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 printed circuit board (PCB) designed to meet the physical requirements of the controller or GUI.

[0067] Headspace Composition Tracking

[0068] The headspace sampler according to the present invention is particularly suitable for monitoring over time the composition of the headspace of a container, referred to herein as a reactor. 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 times 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] The quantification may comprise the comparison of a chromatogram of the volatile species or the targeted 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 produced under the same conditions.

[0071] The sampling is preferably carried out several times during the reaction. A person skilled in the art is able to define the number of samples, the duration during which the samples are carried out, and / or the frequency of the samples as a function of various parameters such as the size of the reactor, the nature of the chemical reaction being monitored, and / or the nature of the species(s) whose quantity is being analyzed.

[0072] Sampling can be carried out at a fixed frequency throughout the reaction. On the contrary, the sampling frequency can be adapted during the monitoring of the reaction depending in particular on the results of the quantification of the previous sampling(s).

[0073] In one embodiment, after each sampling during the monitoring of the chemical reaction, a volume of gas equivalent to that which was taken from the reactor during the sampler 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, in particular 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 rate in the gas introduction channel.

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

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

[0076] Examples of gases that may be quantified include, but are not limited to, 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 photochemistry reactions, CO2 electroreduction reactions, dihydrogen production reactions, and more generally any reaction leading to the production of at least one permanent gas.

[0078] In some embodiments, the chemical reaction that is monitored is a reaction that takes place 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 state of degradation of the battery. The quantity of gases detected can in fact be correlated with the state of degradation of the battery.

[0079] Calibration

[0080] The headspace sampler according to the invention can be used to produce one or more calibration curves for the species whose quantity is analyzed. These curves will depend in particular on the reactor used. Preferably, the establishment of these calibration curves is prior to the implementation of the reaction in the reactor of the headspace sampler according to the invention. They can also be established from the reaction medium, after reaction, by means of a prior purge.

[0081] Operating modes

[0082] The headspace sampler according to the present invention can be used in different operating modes. Among the different modes, we can cite: a. Static mode, which allows to implement a purge sequence and quantification experiments in a closed reactor. The sampling is carried out at defined intervals.

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089]

[0090] b. Flow mode, which allows the implementation of a purge sequence and quantification experiments under a continuous flow of carrier gas. Sampling is performed 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 the container hermetically sealed after injection. d. NMR (nuclear magnetic resonance) mode, which allows a precise quantity (in moles) or volume of gas to be injected into any container, particularly into an NMR tube. In some embodiments, the container is placed at a reduced pressure via a selection valve before the gas is injected. e. Calibration mode, which allows the injection of a precise quantity of a standard gas mixture into a reactor, and the production of a GC chromatogram. This mode can include successive injections / samples, in particular from 2 to 10, in particular 4, successive injections / samples. Reactor purges can be introduced between two consecutive injections / samples. The invention will be better understood by reading the following examples, which are presented for illustrative and non-limiting purposes of the invention. Examples Example 1: Sampler according to the invention and sampling principle [Fig.l] is a schematic diagram of a headspace sampler according to the invention, and illustrates its configuration for monitoring an electrolysis reaction. Each sampling with the sampler of [Fig.l] is implemented as follows: has. Pressure equalization: The reactor pressure is adjusted to a sample 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 time sufficient to purge the inlet line. The position of the inlet valve (2) is then changed to allow gas to re-enter the reactor until the reactor pressure, measured by the pressure gauge, is equal to the sample pressure value. The position of the inlet valve (2) is then moved again, isolating the reactor. b. Sample transfer: The reactor is left to equilibrate at the draw pressure for a fixed duration, typically in the order of 4 to 10 seconds. During this time, the loop valve (1) is closed to isolate the transfer line from the vacuum source. Once the equilibration time has passed, the position of the sampling valve (4) is changed, thus connecting the transfer line to the reactor headspace. Pressure equilibration then drives 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 being thus injected into the inlet port of the gas chromatography apparatus.

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

[0094] The sampler of [Fig. 1] can be used for the production of calibration curves as detailed below from external standards under conditions identical to those used during the implementation of the reaction. Thus, the headspace sampler according to the invention makes it possible to inject known quantities of standard gas into the headspace of the reactor using the corresponding mixtures of standard gases. The production of calibration curves from a mixture of standard gases is carried out 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 predefined value. The predefined value is determined based on the volume of standard gas mixture that is to be added, so that when the standard gas mixture is added the final pressure within the reactor remains below atmospheric pressure.

[0097] b. Adding the standard gas mixture:

[0098] The controller sets a flow rate on one or both flow controllers gas flow rate simultaneously for a time sufficient to purge the gas introduction 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 is equal to 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 equilibrated 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 sample pressure for a few seconds. The loop valve (1) is closed to isolate the transfer line between the reactor and the sample loop from the vacuum source. Once equilibrium is reached, the sample valve (4) is opened, connecting the transfer line to the reactor headspace. The pressure will quickly equilibrate in the two compartments.

[0103] e. Injection into GC:

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

Claims

Claims

1. A headspace sampler, 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 suitable for connection to an inlet of a gas chromatograph, d. A sample loop outlet channel allowing the sample loop and transfer line to be placed at a desired pressure, such as vacuum or atmospheric pressure, e. A reactor outlet channel, f. An inlet valve (2) located between the reactor and the gas introduction 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 for acting on at least one gas flow controller and / or at least one valve of the sampler.

2. A headspace sampler according to claim 1, further comprising a sensor for the pressure within the reactor, said sensor for the pressure being connected to the controller of the sampler.

3. A 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 an outlet at atmospheric pressure.

4. Headspace sampler according to any one of claims 1 to 3, wherein the gas introduction channel comprises at least two channels for introducing 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. A 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. A 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, comprising 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 photochemistry reaction, a hydrogen 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 a predetermined amount of material of a gas or gas mixture.

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