WO2021181211A1

WO2021181211A1 - A kit for volumetric measurements of gas adsorption

Info

Publication number: WO2021181211A1
Application number: PCT/IB2021/051769
Authority: WO
Inventors: Valentina CROCELLÀ; Cesare ATZORI; Giulio LATINI; Matteo SIGNORILE
Original assignee: Università Degli Studi Di Torino
Priority date: 2020-03-09
Filing date: 2021-03-03
Publication date: 2021-09-16
Also published as: IT202000005014A1

Abstract

Described herein is a kit (1;100) for volumetric measurements of gas adsorption, comprising: - a tubular cell (2; 102) having an internal volume (V2) configured for receiving and housing a sample (S) to undergo measurement of adsorption; and - a conditioning jacket (3; 103) coupled to said tubular cell (2; 102) and defining a conditioning volume (V3; V103) designed to contain said tubular cell (2; 102), said conditioning jacket (3; 103) being designed to house a thermostatic fluid within said conditioning volume (V3; V103) and to surround said tubular cell (2; 102), and further comprising a first flow port (8; 108) for said thermostatic fluid and a second flow port (10; 110) for said thermostatic fluid. The conditioning jacket (3; 103) comprises: - a first vessel (4; 104) coupled to said tubular cell (2; 102); and - a second vessel (6; 106), which can be coupled to said first vessel (4; 104) so as to define the conditioning jacket (3; 103) and said conditioning volume (V3; V103).

Description

"A kit for volumetric measurements of gas adsorption"

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TEXT OF THE DESCRIPTION

Field of the invention

The present invention relates to measurements of adsorption of gases on a surface. In particular, the invention has been developed with reference to equipment that can be used for making the measurement itself.

Prior art and general technical problem

Measurements of gas adsorption enable characterization of the materials in regard to the capacity of adsorbing a gaseous phase. Measurements of adsorption are made in isothermal conditions. For applications of technological interest, the temperatures involved typically fall within the range of from 0°C to 90°C.

The sample being measured is introduced into a tubular cell having a tubular portion and an ampoule at the end thereof, so that the latter will receive the sample. The sample is activated by heating the tubular cell set in a position corresponding to the ampoule, and then a vacuum is created therein so as that it is possible to determine the mass of the sample net of any gas previously trapped in the sample itself. The tubular cell comprises a flow port, by means of which it can be connected to equipment for volumetric measurement of adsorption and which can be closed by means of a porous diaphragm that does not allow maintenance of the vacuum, but is impervious with in regard to gases such as nitrogen. For this reason, after application of the vacuum that leads to the measurement of mass of the sample, it is necessary to introduce nitrogen into the tubular cell in order to preserve activation of the sample. This is followed by the step of measurement of the dead volume, i.e., of the volume internal to the tubular cell net of the volume of the sample: this is carried out by evacuating the nitrogen from the tubular cell and introducing helium (which is not adsorbable), which is expressly used for the measurement. The measurement of the dead volume is made at the same temperature as that of the subsequent measurement of volumetric adsorption in so far as the latter is a function of the temperature.

After activation of the sample described above, it is possible to start the measurement, which consists in detecting the adsorbed amount of gas expressed in moles per unit mass of the sample, where the measurement consists in a series of acquisitions at progressively increasing pressures of the adsorbable gas.

The entire measurement step requires a very fine control of temperature, which must be maintained strictly constant in order not to render the measurement itself (which may even last a few days) altogether fruitless. Currently, the thermal conditioning of the sample is performed with thermoelectric elements (e.g., Peltier cells) or again with laboratory ovens or furnaces. The problem inherent in such kinds of devices is the scant possibility of control of the temperature with the required precision, as against non-negligible costs. Considering, for example, a laboratory oven or furnace, this has an operating range of temperatures of between 0°C and 1000°C, whereas the range of temperatures of interest extends for less than one tenth of the above range (0°C to 90°C). As occurs whenever an instrument with a wide operating range is used over a very limited operating range and, moreover, in the proximity of one of the operating extremes, the repeatability of the performance is extremely poor, and the measurement of adsorption that is obtained proves markedly vitiated even if an exemplary procedure of activation of the sample is resorted to.

Object of the invention

The object of the present invention is to solve the technical problems mentioned previously. In particular, the object of the present invention is to provide a kit for volumetric measurements of adsorption that will enable a precise and optimal control of the measurement temperature and will consequently enable measurements to be obtained that are appreciably more accurate than the ones that can be obtained with known measurement kits.

Summary of the invention

The object of the present invention is achieved by a measurement kit having the features forming the subject of the claims that follow, which form an integral part of the technical disclosure provided herein in relation to the invention.

Brief description of the figures

The invention will now be described with reference to the annexed figures, which are provided purely by way of non-limiting example and in which:

- Figure 1 is a cross-sectional view of a kit for volumetric measurements of adsorption according to a first embodiment of the invention; and

- Figure 2 is a cross-sectional view of a kit for volumetric measurements of adsorption according to a second embodiment of the invention.

Detailed description

The reference number 1 in Figure 1 designates as a whole a kit for volumetric measurements of adsorption of gas according to a first embodiment of the invention.

The kit 1 comprises a tubular cell 2 having an internal volume V2 configured for receiving and housing a sample S of material to be subjected to measurement of volumetric adsorption. The tubular cell 2 may, for example, be provided as a container with an end ampoule (as is the case of the preferred embodiment illustrated herein), such as a burette, or again as a cylindrical tubular body with a closed end without appreciable variation of geometry and/or cross section.

According to the invention, the kit 1 further comprises a conditioning jacket 3 coupled to the tubular cell 2 and defining a conditioning volume V3 designed to contain the tubular cell 2. Preferentially, the tubular cell 2 and the conditioning jacket 3 are coaxial and share a longitudinal axis XI of the kit 1.

The conditioning jacket comprises, according to the invention, a first vessel 4 coupled to the tubular cell 2 and a second vessel that can be coupled to the vessel 2 so as to define the conditioning jacket 3 and the conditioning volume V3. In other words, according to the invention, the conditioning jacket 3 is provided in a dismountable way. The tubular cell 2 and the vessels 4 and 6 are preferably made of glass. In this regard, the first vessel 4 is preferably built integral with the tubular cell 2 by means of welding thereof around the tubular cell itself, where welding is carried out hot by creating a localized melting of the glass at the interface between them.

The conditioning jacket 3 is designed to house a thermostatic fluid within the conditioning volume V3 and to surround the tubular cell 2. For this purpose, the conditioning jacket 3 comprises a first flow port 8 for the thermostatic fluid, in particular an inlet port, and a second flow port 10 for the thermostatic fluid, in particular a discharge port. The first flow port 8 is provided on the second vessel 6, whereas the second flow port 10 is provided on the first vessel 4. Advantageously, even though this is an optional characteristic, the conditioning jacket 3 comprises a third flow port 12, preferably provided on the first vessel 4, which defines a release port for emptying the conditioning volume. For this purpose, preferably installed on the port 12 is a tap (not illustrated) by means of which it is possible to govern discharge of the conditioning volume at the end of the measurement. The flow ports 8, 10, 12 may be provided in any angular position about the axis X100, according to the needs.

Also the tubular cell 2 comprises an inlet 14 (which itself defines a flow port for the tubular cell 2: for this reason, in what follows it will be at times referred to as "port" 14) located at a free end of a tubular body 16 of the tubular cell itself. The tubular body 16 traverses the conditioning jacket 3, in particular the vessel 4 at the point of welding thereof to the tubular cell 2, giving out in an area corresponding to the port 14.

At the end of the tubular body 16 opposite to the one where the port 14 is located an ampoule 18 is provided having an internal volume VI8 designed to contain the sample S. The port 14 functions as flow port for the sample S, as well as for all the gases used during the step of activation of the sample itself. Preferentially, the tubular cell 2 develops in such a way that the tubular body 16 is centred on the axis XI.

In the preferred embodiment illustrated here, each of the vessels 4 and 6 has, at the respective free end, a connection flange by means of which the conditioning jacket 3 can be installed.

In detail, the vessel 4 comprises a first connection flange 20, and the vessel 6 comprises a second connection flange 22. The connection flanges 20, 22 are arranged axially facing one another and with a joining element 24 set in between. The joining element 24 comprises a positioning ring, the end circular rims of which are configured for bearing upon the flanges 20, 22 in the area where the latter are bent outwards, thus guaranteeing automatic centring of the vessels 4 and 6. The joining element 24 further comprises an annular seal 28 set on the periphery of the ring 26 and set between the flanges 20, 22 themselves so as to guarantee liquid tightness within the conditioning volume V3. It should be noted that the joining element 24 creates a minimum axial distancing of the vessels 4 and 6, in such a way that the conditioning volume V3 is greater than the sum of respective internal volumes V4 (vessel 4) and V6 (vessel 6), the difference being due to the volume corresponding to the axial band covered by the seal 28.

Maintenance of the vessels 4, 6 in a coupled position is ensured, in the preferred embodiment illustrated here, by means of a fastening element 28 set coupled astride of the flanges 20, 22.

Operation of the kit 1 is described in what follows. The kit 1 is configured for connection to an instrument for volumetric measurement of adsorption through the port 14. The latter functions as inlet for the sample S and as bi-directional flow port for the fluids used in the process of activation of the sample S. Once again at the port 14 a plug may be inserted, which bears a porous diaphragm to be used at the end of each step of administration of gas into the tubular cell 2 or subtraction of gas therefrom.

During the volumetric measurement of adsorption, the sample S in the ampoule 18 - and the tubular cell 2 as a whole - are thermally conditioned by means of the conditioning jacket 3, namely by introduction of a thermostatic fluid through the port 8, while the port 10 enables discharge of the liquid towards a tank drawing from which is a circulation pump, which in turn sends the liquid back to the port 8. Examples of liquids that can be used in the kit 1 include water, ethylene glycol, ethanol, silicone oil, and mixtures thereof.

The flow rate of liquid in the conditioning volume V3 is regulated so as to maintain the temperature of the sample S as constant as possible. At the end of the measurement, the conditioning liquid is discharged from the volume V3 through the port 12, if this is envisaged. Otherwise, the liquid is drained through the port 8 by disconnecting the port 10 from the circuit for supply of the conditioning liquid.

Unlike known thermal-conditioning solutions, the temperature of the sample S is maintained in an extremely precise way thanks to the thermal conditioning carried out via the conditioning jacket. In this sense, the convective thermal exchange between the thermostatic fluid and the tubular cell 2 is far easier to control and far easier to manage than a thermal conditioning carried out by means of an oven or a thermoelectric element. In the first case, an oven has a size considerably greater than that of the tubular cell 2, which - combined with the fact that the range of temperatures is excessively wide as compared to the window of interest - results in an extremely poor controllability of the volumetric distribution of temperature. In the second case, a thermoelectric heating element is likely to generate marked lack of uniformity of the thermal field that impinges upon the tubular cell 2, with the danger of perturbing the measurement even more. None of the above disadvantages arise in the case of the kit 1: the ease of controllability of the temperature obtained by acting on the flow rate and on the type of thermostatic fluid, together with the favourable volumetric ratio between the conditioning jacket 3 and the tubular cell 2, provide an immediate and accurate control of the temperature. In this connection, the best results are obtained if the ratio between the volume V3 and the volume V2 of the tubular cell 2 (also including the volume V18 of the ampoule 18) satisfies the following condition: 3.5 < V3/V2 < 5.

With reference to Figure 2, the reference number 100 designates as a whole a kit for volumetric measurements of gas adsorption according to a second embodiment of the invention.

The kit 100 differs from the kit 1 basically in the structure of the tubular cell 2 and in the connections of the latter with the external environment.

The kit 100 comprises a tubular cell 102 having an internal volume V102 configured for receiving and housing the sample S of material to undergo measurement of volumetric adsorption.

The kit 100 further comprises a conditioning jacket 103 coupled to the tubular cell 102 and defining a conditioning volume V103 designed to contain the tubular cell 102. Preferentially, the tubular cell 102 and the conditioning jacket 103 are coaxial and share a longitudinal axis X100 of the kit 100.

The conditioning jacket 103 comprises, like the jacket 3, a first vessel 104 coupled to the tubular cell 102 and a second vessel 106 that can be coupled to the vessel 104 so as to define the conditioning jacket 103 and the conditioning volume V103. The conditioning jacket 103 is hence provided in a dismountable way. The tubular cell 102 and the vessels 104 and 106 are preferably made of glass. In this regard, the first vessel 104 is preferably built integral with the tubular cell 102 by being welded around the tubular cell itself, where welding is performed in hot conditions to create a localized melting of the glass at the interface between them.

The conditioning jacket 103 is designed to house a thermostatic fluid within the conditioning volume V103 and to surround the tubular cell 2. For this purpose, the conditioning jacket 103 comprises a first flow port 108 for the thermostatic fluid, in particular an inlet port, and a second flow port 110 for the thermostatic fluid, in particular a discharge port. The first flow port 108 is provided on the second vessel 106, whereas the second flow port 110 is provided on the first vessel 104. Advantageously, even though this is an optional feature, the conditioning jacket 3 comprises a third flow port 112, preferably provided on the first vessel 104, which defines a release port for emptying the conditioning volume. For this purpose, preferably installed on the port 112 is a tap T, by means of which it is possible to govern discharge of the conditioning volume at the end of the measurement.

The tubular cell 102 comprises an inlet 114 (which itself defining a flow port for the tubular cell 102: for this reason, in what follows it will be at times referred to as "port" 114) located at a free end of a tubular body 116 of the tubular cell itself.

The tubular body 116 traverses the conditioning jacket 3, in particular the vessel 104 at the point of welding thereof to the tubular cell 102, giving out in an area corresponding to the port 114. Unlike the tubular cell 2, the tubular body 116 does not extend along the axis X100, but comprises a first portion 116A and a second portion 116B incident with one another, in particular orthogonal to one another. In particular, the tubular body 116 of the tubular cell 102 presents an elbow EBW inside the conditioning jacket 103 where the tubular body 116 deviates from the portion 116A, which extends centred on, or at least in a direction parallel to, the axis X100 (which is a main direction of extension for the kit 1), to the portion 116B.

The port 114 is provided on a further tubular body of the tubular cell 102 incident on the tubular portion 116B. The tubular body in question extends along an axis X114 preferentially parallel to the axis X100. At the intersection between the tubular body that bears the port 114 and the tubular portion 116B, a jacket 117 is moreover provided, rotatably mounted within which is a moving element V, which is driven in rotation by means of a knob K. The moving element 117 defines a vacuum tap, i.e., a tap configured for maintaining the vacuum in the tubular cell 102 once it has been applied therein. For this purpose, the moving element V is set downstream of the port 114 so that, even when the plug P with porous diaphragm is applied thereon, the internal volume of the tubular cell 102 is in any case isolated from fluid communication with the outside world.

As in the case of the tubular cell 2, at the end of the tubular body 116 opposite to the one where the port 114 is located, an ampoule 118 is provided having an internal volume VI8 designed to contain the sample

S.

In the preferred embodiment illustrated here, each of the vessels 104 and 106 has, at the respective free end, a flange connection by means of which the conditioning jacket 103 can be installed.

In detail, the vessel 104 comprises a first connection flange 120 and the vessel 6 comprises a second connection flange 122. The connection flanges 120, 122 are arranged axially facing one another, with a joining element 124 set in between. The joining element 124 is preferably identical to the joining element 24 and comprises a positioning ring 126, the circular end rims of which are configured to bear upon the flanges 120, 122 in the area where the latter are bent outwards, thus guaranteeing automatic centring of the vessels 104 and 106. The joining element 124 further comprises an annular seal 128 set on the periphery of the ring 126 and between the flanges 120, 122 themselves so as to guarantee liquid tightness within the conditioning volume V3. It should be noted that the joining element 124 creates a minimum axial distancing of the vessels 104 and 106 so that the conditioning volume V103 is greater than the sum of the respective internal volumes V104 (vessel 104) and V106 (vessel 106), the difference being due to the volume corresponding to the axial band covered by the seal 128.

As in the case of the vessels 4 and 6, maintenance of the vessels 104, 106 in a coupled position is ensured, in the preferred embodiment illustrated here, by means of a fastening element 128 that is set coupled astride of the flanges 120, 122.

Operation of the kit 100 is similar to that of the kit 1, except for the further operating possibility bestowed by the structure of the tubular cell 102 and of the port 114. Like the kit 1, the kit 100 is configured for connection to an instrument for volumetric measurement of adsorption through the port 114. The latter functions as inlet for the sample S and as bi-directional flow port for the fluids used in the process of activation of the sample S. At the port 114 it is possible to insert a plug P that bears a porous diaphragm to be used at the end of each step of administration of gas into the tubular cell 102 or subtraction of gas therefrom. However, in the kit 100 it is possible to maintain the vacuum in the tubular cell 102 once it has been created thanks to the valve with the moving element V, which is configured for isolating selectively the port 114 from the internal volume of the tubular cell 102. In this way, the kit 100 further extends the operating range of the kit 1, making it possible to operate with samples S that require more complex activation procedures, for example aggressive chemical species, samples not compatible with inert gases, etc.. In this sense, by turning the moving element V, there ceases the need to fill the tubular cell 102 with nitrogen after the vacuum has been created therein. In any case, the moving element 117 enables isolation of the tubular cell 102 or connection thereof to the equipment for volumetric measurement via the port 114.

During volumetric measurement of adsorption, the sample S in the ampoule 118 - and the tubular cell 102 as a whole - are thermally conditioned by means of the conditioning jacket 103, namely by means of introduction of a thermostatic fluid through the port 108, while the port 110 enables discharge of the liquid towards a tank from which it is drawn by a circulation pump, which in turn sends the liquid back to the port 108.

The flow rate of liquid in the conditioning volume V103 is regulated so as to maintain the temperature of the sample S as constant as possible. At the end of the measurement, the conditioning liquid is discharged from the volume V103 through the port 112, if the latter is envisaged. Otherwise, the liquid is drained off through the port 108 by disconnecting the port 110 from the circuit for supply of the conditioning liquid.

There remain of course all the technical advantages already described for the kit 1, with the additional advantage - in the light of the foregoing description - of an extension of the operating possibilities without any need for accessories.

Of course, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated herein, without thereby departing from the scope of the present invention, as defined by the annexed claims.

Claims

1. A kit (1; 100) for volumetric measurements of gas adsorption, comprising:

- a tubular cell (2; 102) having an internal volume (V2) configured for receiving and housing a sample (S) to undergo measurement of adsorption; and

- a conditioning jacket (3; 103) coupled to said tubular cell (2; 102) and defining a conditioning volume (V3; V103) designed to contain said tubular cell (2; 102), said conditioning jacket (3; 103) being adapted to house a thermostatic fluid within said conditioning volume (V3; V103) and to surround said tubular cell (2; 102) and further comprising a first flow port (8; 108) for said thermostatic fluid and a second flow port (10; 110) for said thermostatic fluid, said conditioning jacket (3; 103) comprising:

- a first vessel (4; 104) coupled to said tubular cell (2; 102); and

- a second vessel (6; 106), which can be coupled to said first vessel (4; 104) so as to define the conditioning jacket (3; 103) and said conditioning volume (V3; V103).

2. The kit (1; 100) according to Claim 1, wherein said first vessel (4; 104) is provided integral with said tubular cell (2; 102).

3. The kit (1; 100) according to Claim 1 or Claim

2, wherein said second flow port (10; 110) is provided on said first vessel (4; 104), and wherein said first flow port (8; 108) is provided on said second vessel

(6; 106).

4. The kit (1; 100) according to any one of the preceding claims, wherein said tubular cell (2; 102) comprises a tubular body (16; 116, 116A, 116B) and an ampoule (18; 118), said ampoule (18; 118) being designed to house said sample (S), and wherein said tubular portion (16; 116, 116A, 116B) traverses said conditioning jacket (3; 103) giving out at a third flow port (14; 114).

5. The kit (1; 100) according to any one of the preceding claims, wherein, named V3 the value of the conditioning volume, and named V2 the value of the volume of said tubular cell, the following relation applies: 3.5 < V3/V2 < 5.

6. The kit (100) according to Claim 4, wherein said tubular body (116) comprises a first portion (116A), which extends along a main direction of extension (X100) of said conditioning jacket (103), an elbow (EBW) inside said conditioning volume (V103), and a second portion (116B), which extends in a direction incident with said main direction of extension (X100) of the conditioning jacket (103), wherein said first portion (116A) and said second portion (116B) are joined at said elbow (EBW), and wherein said second portion (116B) traverses said conditioning jacket (103) and gives out at said third flow port (114).

7. The kit according to Claim 6, wherein the third flow port (114) can be selectively isolated from said tubular body (116) of the tubular cell (102) by means of a valve (117, V, K).

8. The kit according to Claim 7, wherein said valve (117, V, K) comprises a mobile unit (V) operable in rotation by means of a knob (K), said mobile unit being configured for exerting a fluid tight action when said third flow port (114) is isolated from said tubular body (116).

9. The kit (1; 100) according to any one of the preceding claims, wherein:

- the first vessel (4; 104) comprises a first connection flange (20; 120); and

- the second vessel (6; 106) comprises a second connection flange (22; 122) facing said first connection flange, said first connection flange (20; 120) and said second connection flange (22; 122) having an interposed connection element (24; 124) and being connected by a fastening element (30; 130).

10. The kit (1; 100) according to Claim 9, wherein said joining element (24; 124) comprises a positioning ring configured for bearing upon said first and second connection flanges (20, 22; 120, 122) and an annular seal set on the periphery of said positioning ring (26; 126).