METHOD FOR PREPARING A MONOLITHIC NANOPOROUS SILICATE SOL-GEL MATERIAL

Abstract

A method for preparing a monolithic nanoporous silicate sol-gel material for modulating the pore size distribution for one single starting composition without the addition of a structuring agent. The method includes the following steps: a) synthesising a gel from at least one organosilylated precursor, the synthesis being carried out in an aqueous medium, optionally including an organic solvent and without a structuring agent, and b) drying the gel obtained in step a) at a temperature between 10° C. and 70° C., preferably between 15° C. and 55° C. and more preferably between 20° C. and 40° C., in a gas flow in a drying chamber to obtain a monolithic nanoporous silicate sol-gel material and a residual relative humidity in the drying chamber of between 0.1 and 20%, preferably between 0.5 and 10% and more preferably about 5%.

Claims

1-9. (canceled)

10. A process for preparing monolithic nanoporous silicate sol-gel material, said process comprising the following steps: a) synthesizing a gel from at least one organosilyl precursor, the synthesis being carried out in aqueous medium optionally comprising an organic solvent and without structuring agent, b) drying the gel obtained in step a) at a temperature of between 10° C. and 70° C., in a stream of gas in a drying chamber until a monolithic nanoporous silicate sol-gel material is obtained and the residual relative humidity in the drying chamber is between 0.1% and 20%.

11. The process as claimed in claim 10, wherein the drying step b) is carried out at a temperature of between 15° C. and 55° C.

12. The process as claimed in claim 10, wherein the drying step b) is carried out at a temperature of between 20° C. and 40° C.

13. The process as claimed in claim 10, wherein the residual relative humidity in the drying chamber in step b) is between 0.5% and 10%.

14. The process as claimed in claim 10, wherein the residual relative humidity in the drying chamber in step b) is about 5%.

15. The process as claimed in claim 10, wherein the synthesis is carried out without acidic or basic catalyst.

16. The process as claimed in claim 10, wherein the at least one organosilyl precursor is selected from tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, a fluoroalkyltrimethoxysilane, a fluoroalkyltriethoxysilane, a chloroalkyltrimethoxysilane, a chloroalkyltriethoxysilane, an alkyltrimethoxysilane, an alkyltriethoxysilane, an aminopropyltriethoxysilane, an aminopropyltrimethoxysilane and mixtures thereof.

17. The process as claimed in claim 10, wherein the organic solvent is a C.sub.1 to C.sub.6 aliphatic alcohol.

18. The process as claimed in claim 10, wherein the organic solvent is methanol or ethanol.

19. The process as claimed in claim 10, wherein the organic solvent is methanol.

20. The process as claimed in claim 10, wherein the drying step is carried out in a stream of dry gas.

21. The process as claimed in claim 10, wherein the drying step comprises applying a stream of wet gas.

22. The process as claimed in claim 15, wherein the drying step is carried out in stages of humidity.

23. The process as claimed in claim 10, wherein the drying step is carried out at a temperature of between 15° C. and 25° C.

24. The process as claimed in claim 10, wherein the drying step is carried out at a temperature of about 20° C.

25. The process as claimed in claim 10, wherein the drying step is carried out at a temperature of between 30° C. and 50° C.

26. The process as claimed in claim 10, wherein the drying step is carried out at a temperature of about 40° C.

Description

FIGURES

[0035] FIG. 1: Surface pore size distribution for materials based on TMOS; comparison of examples 1, 2, 3 and 4.

[0036] FIG. 2: Surface pore size distribution for materials based on TMOS/MeTMOS; comparison of examples 5 and 6.

[0037] FIG. 3: Surface pore size distribution for materials based on TMOS/APTES (0.99/0.01); comparison of examples 7, 8, 9 and 10.

[0038] FIG. 4: Surface pore size distribution for materials based on TMOS/APTES (0.97/0.03); comparison of examples 11, 12, 13 and 14.

[0039] FIG. 5: Surface pore size distribution for materials based on TMOS/APTES (0.80/0.20); comparison of examples 15, 16 and 17.

[0040] FIG. 6: Surface pore size distribution for materials based on TMOS/PhTMOS (0.90/0.10); comparison of examples 18, 19 and 20.

[0041] FIG. 7: Measurement of release kinetics in static mode of toluene trapped in the material of example 6. A) profile of spectral change during the release time. B) the dots (⋅) correspond to the variation in the absorbance of toluene at a given wavelength (203.9 nm) over time, and the dashed line (---) corresponds to the correlation with exponential growth kinetics with a plateau (Abs(toluene)=a(1-exp(-bt)) for determining the release rate, V, with V=a*b.

[0042] FIG. 8: Correlation between the toluene release rate and the percentage microporosity of the materials of examples 2, 6, 7, 8, 11 and 12. Each dot corresponds to the release rate determined as described in FIGS. 7A and 7B.

[0043] FIG. 9: Change in the absorbance of naphthalene trapped in the material of example 7 as a function of the release time, in static mode.

[0044] FIG. 10: Release kinetics of naphthalene trapped in the material of example 7, in static mode.

[0045] FIG. 11: Correlation between the toluene release rate and the percentage microporosity of the materials of examples 2, 3 and 7.

[0046] FIG. 12: Release kinetics in dynamic mode of toluene with the material of example 4 doped for 2 h with the saturation vapor of toluene.

EXAMPLES

[0047] The examples given here correspond to syntheses performed from organosilyl precursors which are widely used for sol-gel materials, such as tetramethoxysilane (TMOS), methyltrimethoxysilane (MeTMOS), phenyltrimethoxysilane (PhTMOS) or else 3-aminopropyltrimethoxysilane (APTES) and from binary mixtures thereof (TMOS/MeTMOS, TMOS/PhTMOS, TMOS/APTES).

[0048] For each formulation, the synthesis was carried out without providing acidic or basic catalyst. The sol prepared from the reactants is poured either into individual parallelepipedal molds (polypropylene spectrophotometric cells with dimensions of 40*10*4 mm) or into molds comprising parallelepipedal wells (with dimensions of 16*10*4 mm). For drying, the mold is placed in a desiccator serving as a drying chamber, equipped with an inlet and an outlet for a sweep of drying gas stream. The interior of the drying chamber is likewise provided with a humidity indicator. As soon as the sol is converted into a gel, a precise drying protocol is applied. Depending on the drying protocols, it is possible to vary the pore size distribution of the materials originating from a given initial formulation.

[0049] When drying is carried out at 40° C., a similar device is placed in an oven heated at 40° C. The gas (dry or wet) sweeping the device is heated at 40° C.

Example 1

[0050] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%), MeOH (CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.792 g.Math.cm.sup.−3, purity 99.8%), deionized H.sub.2O.
Formulation: TMOS/MeOH/H.sub.2O=1/4/4 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 11.7 mL of TMOS and 12.7 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. 5.7 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 5 minutes at ambient temperature in the effectively closed flask. The solution is poured into polypropylene molds, which are covered hermetically with an aluminum membrane. In example 1, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).
Drying protocol: The cells are placed in a closed glass chamber (desiccator) as described above. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. At this point the aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of dry argon at 300 mL/min and at ambient temperature. When the humidity indicator indicates a relative humidity (RH) of 5% in the drying chamber, drying is halted. The total drying time is 8 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 2

[0051] The reactants, the mode of synthesis and the molds used here are the same as for example 1. Only the mode of drying is different.
Formulation: TMOS/MeOH/H.sub.2O=1/4/4 in molar proportion.
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. At this point the aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at ambient temperature and a RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 15 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 3

[0052] The reactants and the mode of synthesis used here are the same as those described in example 1. In example 3, the polypropylene mold is a multiwell plate, each well being a parallelepiped with dimensions of 4*10*16 mm The drying temperature differs from example 1.
Formulation: TMOS/MeOH/H.sub.2O=1/4/4 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 56.4 mL of TMOS and 61.3 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. 27.3 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 5 minutes at ambient temperature in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. At this point the aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of dry argon at a temperature of 40° C. Drying is halted when an RH of 5% is reached in the chamber. The total drying time is 7 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 4

[0053] The reactants, the mode of synthesis and the multiwell mold used here are the same as those described in example 3. Only the drying is different.
Formulation: TMOS/MeOH/H.sub.2O=1/4/4 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 56.4 mL of TMOS and 61.3 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. 27.3 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 5 minutes at ambient temperature in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. At this point the aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at a temperature of 40° C. and an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber.
The total drying time is 14 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 1, 2, 3 and 4 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface areas of adsorption were established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 1, 2, 3 and 4 are reported in FIG. 1.

Example 5

[0054] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); methyltrimethoxysilane (MeTMOS, CAS: 1185-55-3, molar mass=136.22 g.Math.mol.sup.−1, d=0.955 g.Math.cm.sup.−3, purity 98%); methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/MeTMOS/MeOH/H.sub.2O=0.90/0.10/4.02/4.06 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 10.5 mL of TMOS, 1.1 mL of MeTMOS and 12.7 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. 5.7 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 5 minutes at ambient temperature in the effectively closed flask. The solution is subsequently poured into a polypropylene mold, which is covered hermetically with an aluminum membrane. In example 5, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of dry argon at 300 mL/min and at ambient temperature. When the humidity indicator indicates a relative humidity (RH) of 5%, drying is halted. The total drying time is 8 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 6

[0055] The reactants and the mode of synthesis applied here are the same as those for example 5. In example 6, the mold is a multiwell plate, each well being a parallelepiped with dimensions of 4*10*16 mm The drying temperature differs from example 5.
Formulation: TMOS/MeTMOS/MeOH/H.sub.2O=0.90/0.10/4.01/4.03 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 50.8 mL of TMOS, 5.4 mL of MeTMOS and 61.4 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. 27.4 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 5 minutes at ambient temperature in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon heated at 40° C. When the humidity indicator in the drying chamber indicates a relative humidity of 80%, the humidity of the stream is lowered to 50%. Drying is continued with a subsequent stage at 30% humidity, whereupon a stream of dry air is applied until a relative humidity of 5% is obtained in the chamber. The total drying time is 12 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 5 and 6 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface areas of adsorption were established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 5 and 6 are reported in FIG. 2.

Example 7

[0056] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); 3-aminopropyltrimethoxysilane (APTES, CAS: 919-30-2, molar mass=221.37 g.Math.mol.sup.−1, d=0.946 g.Math.cm.sup.−3, purity 99%), methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.99/0.01/5.00/4.00 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 10.4 mL of TMOS, 0.2 mL of APTES and 14.3 mL of methanol, which are then mixed with magnetic stirring for 5 minutes.

[0057] The mixture is cooled in a bath containing ethanol and liquid nitrogen to −25° C. before the water is added. 5.1 mL of deionized water are added to the mixture, which is subsequently stirred for 2 minutes in the effectively closed flask. The solution is poured into polypropylene molds, which are covered hermetically with an aluminum membrane. In example 7, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).

Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of dry argon at 300 mL/min and at ambient temperature. When the humidity indicator indicates a relative humidity (RH) of 5% in the chamber, drying is halted. The total drying time is 7 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 8

[0058] The reactants, the mode of synthesis and the molds used here are the same as for example 7. Only the volume (50 mL) and the mode of drying are different.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.99/0.01/5.00/4.00 in molar proportion.
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at ambient temperature. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 35 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 9

[0059] The reactants and the mode of synthesis used here are the same as those described in example 7. In example 9, the mold is a multiwell plate, each well being a parallelepiped with dimensions of 4*10*16 mm The drying temperature differs from example 7.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.99/0.01/5.01/4.02 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 50.3 mL of TMOS, 0.80 mL of APTES and 69.2 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. The mixture is cooled in a bath containing ethanol and liquid nitrogen to −25° C. before the water is added. 24.7 mL of deionized water are added to the mixture, which is subsequently stirred for 2 minutes in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of dry argon at 40° C. When the humidity indicator in the chamber indicates a relative humidity of 5%, drying is halted. The total drying time is 6 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 10

[0060] The reactants, the mode of synthesis and the multiwell mold used here are the same as for example 9. Only the drying is different.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.99/0.01/5.01/4.02 in molar proportion.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon heated at 40° C. and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 14 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 7, 8, 9 and 10 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface areas of adsorption were established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 7, 8, 9 and 10 are reported in FIG. 3.

Example 11

[0061] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); 3-aminopropyltrimethoxysilane (APTES, CAS: 919-30-2, molar mass=221.37 g.Math.mol.sup.−1, d=0.946 g.Math.cm.sup.−3, purity 99%), methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.97/0.03/5.00/4.01 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 10.2 mL of TMOS, 0.50 mL of APTES and 14.3 mL of methanol, which are then mixed with magnetic stirring for 5 minutes. The mixture is cooled to −30° C. (bath of ethanol and liquid nitrogen) before the water is added. 5.1 mL of deionized water are added to the mixture. The mixture is subsequently stirred for 2 minutes in the effectively closed flask. The solution is poured into polypropylene molds, which are covered hermetically with an aluminum membrane. In example 11, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of dry argon at 300 mL/min and at ambient temperature. When the humidity indicator indicates a relative humidity (RH) of 5%, drying is halted. The total drying time is 16 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 12

[0062] The reactants, the mode of synthesis and the molds used here are the same as for example 11. Only the mode of drying is different.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.97/0.03/5.00/4.01 in molar proportion.
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at ambient temperature and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 21 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 13

[0063] The reactants and the mode of synthesis used here are the same as those described in example 11. In example 13, the mold is a multiwell plate, each well being a parallelepiped with dimensions of 4*10*16 mm The mold is covered hermetically with an aluminum membrane. The drying temperature differs from example 11.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.97/0.03/5.01/4.02 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 49.1 mL of TMOS, 2.39 mL of APTES and 68.9 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. The mixture is cooled in a bath containing ethanol and liquid nitrogen to −30° C. before the water is added. 24.6 mL of deionized water are added to the mixture, which is subsequently stirred for 2 minutes in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of dry argon at 40° C. When the humidity indicator in the chamber indicates a relative humidity of 5%, drying is halted. The total drying time is 7 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 14

[0064] The reactants, the mode of synthesis and the mold used here are the same as for example 13. The drying temperature is different from example 13.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.97/0.03/5.01/4.02 in molar proportion.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at 40° C. and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 10 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 11, 12, 13 and 14 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface areas of adsorption were established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 11, 12, 13 and 14 are reported in FIG. 4.

Example 15

[0065] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); 3-aminopropyltrimethoxysilane (APTES, CAS: 919-30-2, molar mass=221.37 g.Math.mol.sup.−1, d=0.946 g.Math.cm.sup.−3, purity 99%), methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.80/0.20/5.02/4.00 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 8.1 mL of TMOS, 3.2 mL of APTES and 13.8 mL of methanol, which are then mixed with magnetic stirring for 5 minutes. The mixture is cooled to −40° C. (bath of ethanol and liquid nitrogen) before the water is added. 4.9 mL of deionized water are added to the mixture. The mixture is stirred for 1 minute in the effectively closed flask. The solution is poured into polypropylene molds, which are covered hermetically with an aluminum membrane.
In example 15, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at ambient temperature and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 34 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 16

[0066] The reactants and the mode of synthesis used here are the same as those described in example 15. In example 16, the mold is a multiwell plate, each well being a parallelepiped with dimensions of 4*10*16 mm The drying temperature differs from example 15.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.80/0.20/5.02/4.03 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 39.2 mL of TMOS, 15.4 mL of APTES and 66.7 mL of methanol, which are then mixed with magnetic stirring for 2 minutes. The mixture is cooled in a bath containing ethanol and liquid nitrogen to −40° C. before the water is added. 23.8 mL of deionized water are added to the mixture, which is subsequently stirred for 2 minutes in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of dry argon at 40° C. When the humidity indicator in the chamber indicates a relative humidity of 5%, drying is halted. The total drying time is 7 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 17

[0067] The reactants, the mode of synthesis and the multiwell mold used here are the same as for example 16. Only the drying is different.
Formulation: TMOS/APTES/MeOH/H.sub.2O=0.80/0.20/5.02/4.03 in molar proportion.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at 40° C. and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 9 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 15, 16 and 17 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface areas of adsorption were established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 15, 16 and 17 are reported in FIG. 5.

Example 18

[0068] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); phenyltrimethoxysilane (PhTMOS, CAS: 2996-92-1, molar mass=198.29 g.Math.mol.sup.−1, d=1.062 g.Math.cm.sup.−3, purity 98%); methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/PhTMOS/MeOH/H.sub.2O=0.90/0.10/6.03/5.98 in molar proportion.
Procedure for 30 mL of sol: A round-bottom flask is charged with 8.0 mL of TMOS, 1.1 mL of PhTMOS and 14.5 mL of methanol. The mixture is heated in a water bath at 60° C. The mixture is subjected to magnetic stirring for 2 minutes and then admixed with 6.4 mL of deionized water. The mixture is subsequently stirred for 3 minutes in the effectively closed flask. The solution is poured into polypropylene molds, which are covered hermetically with an aluminum membrane. In example 18, the polypropylene molds are individual spectrophotometric cells with dimensions of 40*10*4 (mm).
Drying protocol: The cells are placed in a closed glass chamber as described above. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at ambient temperature and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 13 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 19

[0069] Reactants: Tetramethoxysilane (TMOS, CAS: 681-84-5, molar mass=152.22 g.Math.mol.sup.−1, d=1.023 mg.Math.cm.sup.−3, purity>99.9%); phenyltrimethoxysilane (PhTMOS, CAS: 2996-92-1, molar mass=198.29 g.Math.mol.sup.−1, d=1.062 g.Math.cm.sup.−3, purity 98%); methanol (MeOH, CAS: 67-56-1, molar mass=32.04 g.Math.mol.sup.−1, d=0.791 g.Math.cm.sup.−3, purity 99.8%); deionized H.sub.2O.
Formulation: TMOS/PhTMOS/MeOH/H.sub.2O=0.90/0.10/6.02/6.04 in molar proportion.
Procedure for 145 mL of sol: A round-bottom flask is charged with 38.5 mL of TMOS, 5.4 mL of PhTMOS and 69.9 mL of methanol. The mixture is heated in a water bath at 60° C. The mixture is subjected to magnetic stirring for 2 minutes and 31.2 mL of deionized water are added. The mixture is subsequently stirred for 3 minutes in the effectively closed flask. The solution is poured into the multiwell mold, which is covered hermetically with an aluminum membrane.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying.
The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of dry argon at 40° C. When the humidity indicator in the chamber indicates a relative humidity of 5%, drying is halted. The total drying time is 6 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.

Example 20

[0070] The reactants, the mode of synthesis and the multiwell mold used here are the same as for example 19. Only the drying is different.
Formulation: TMOS/PhTMOS/MeOH/H.sub.2O=0.90/0.10/6.02/6.04 in molar proportion.
Drying protocol: The multiwell mold is placed in a closed glass chamber as described above, and heated at 40° C. A humidity indicator is placed in the chamber for monitoring the drying. The drying protocol begins when the sol has gelled. The aluminum membrane is replaced with a porous membrane (AB-0718, Adhesive gas permeable seals, Thermo Scientific).
The chamber is swept with a stream of 300 mL/min of wet argon at 40° C. and at an RH of 80%. When the humidity indicator indicates a relative humidity of 80% in the chamber, the humidity of the stream is lowered to 50%. Drying is continued with a following stage at 30% humidity, whereupon a dry stream is applied until an RH of 5% is obtained in the chamber. The total drying time is 13 days. The dry parallelepipedal monoliths are packaged individually in hermetic bags and stored (between 1 month and 1 year) before being used.
The porosity properties of examples 18, 19 and 20 were determined with the establishment of N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2. The specific surface area of adsorption was established on the basis of a cylindrical pore model using density functional theory (DFT). Table 1 collates this data, and the pore size distributions of the materials of examples 18, 19 and 20 are reported in FIG. 6.

TABLE-US-00001 TABLE 1 Specific surface area of Percentage adsorption, Pore volume of S.sub.DFTeq V.sub.pore micropores Formulation (m.sup.2/g) (cm.sup.3/g) (%) Example 1 TMOS/MeOH/H.sub.2O 890 ± 90 0.53 ± 0.06 58.5 Example 2 1/4/4 840 ± 85 0.47 ± 0.05 63.0 Example 3 890 ± 90 0.68 ± 0.07 40.6 Example 4 860 ± 90 0.61 ± 0.06 37.1 Example 5 TMOS/MeTMOS/MeOH/H.sub.2O 770 ± 80 0.56 ± 0.06 37.9 0.90/0.10/4.02/4.06 Example 6 TMOS/MeTMOS/MeOH/H.sub.2O 840 ± 90 0.62 ± 0.08 36.1 0.90/0.10/4.01/4.03 Example 7 TMOS/APTES/MeOH/H.sub.2O 660 ± 70 0.54 ± 0.06 23.2 Example 8 0.99/0.01/5.00/4.00 480 ± 60 0.71 ± 0.08 0 Example 9 TMOS/APTES/MeOH/H.sub.2O 860 ± 90 0.97 ± 0.10 0 Example 10 0.99/0.01/5.01/4.02 660 ± 70 0.88 ± 0.09 0 Example 11 TMOS/APTES/MeOH/H.sub.2O 690 ± 70 0.64 ± 0.05 4.1 Example 12 0.97/0.03/5.00/4.01 460 ± 55 0.60 ± 0.06 0 Example 13 TMOS/APTES/MeOH/H.sub.2O 930 ± 95 0.99 ± 0.10 0 Example 14 0.97/0.03/5.01/4.02 570 ± 65 0.88 ± 0.09 0 Example 15 TMOS/APTES/MeOH/H.sub.2O 300 ± 40 0.53 ± 0.06 0 0.80/0.20/5.02/4.00 Example 16 TMOS/APTES/MeOH/H.sub.2O 570 ± 65 0.67 ± 0.07 0 Example 17 0.80/0.20/5.02/4.03 350 ± 40 0.48 ± 0.05 0 Example 18 TMOS/PhTMOS/MeOH/H.sub.2O 780 ± 80 0.38 ± 0.04 60.9 0.90/0.10/6.03/5.98 Example 19 TMOS/PhTMOS/MeOH/H.sub.2O 640 ± 70 0.54 ± 0.06 26.9 Example 20 0.90/0.10/6.02/6.04 680 ± 70 0.70 ± 0.08 0

Example 21—Doping and Controlled Release of Volatile Organic Compounds (VOCs)

[0071] One of the applications is the doping and the controlled release of volatile organic compounds (VOCs) depending on the size of the compounds and the pore sizes of the material used.

Doping with Toluene or with Naphthalene

[0072] In each case, the material was doped by a gaseous route with the saturation vapor of the pollutant above the pure liquid (in the case of toluene) or the solid (in the case of naphthalene).
Doping for 25 h: The materials of examples 2, 6, 7, 8, 11 and 12 were doped for 25 h with the saturation vapor of toluene, and the material of example 7 was doped for 25 h in a saturation atmosphere of vapor from solid naphthalene.
Doping for 2 h: The material of example 4 was doped for 2 h with the saturation vapor of toluene, and the materials of examples 2, 3 and 7 were doped for 2 h with the saturation vapor of naphthalene.

Release in Static Mode

[0073] For the static mode release tests, the doped material of example 2 was placed in a closed glass chamber with a volume of 170 mL, containing a quartz spectrophotometer cell. The spectrophotometer is located in an air-conditioned room at 20° C. The rate of release was obtained with the measurement of the absorbance of gaseous pollutant released as a function of the release time. In this case, release is stopped when the equilibrium in concentration between the pollutant in the gas phase and in the material is reached.
FIG. 7A shows the measurements of the absorbance between 200 nm and 300 nm of the toluene released for the material of example 2, for different release times. It is found that the absorbance at 203.9 nm and therefore the concentration of toluene in the atmosphere increases over time, leveling out when the equilibrium in concentration between the toluene in the gas phase and in the material is reached. FIG. 7B shows the change in the absorbance of toluene at 203.9 nm as a function of the release time (black dots) and the correlation of the measurement with kinetics of exponential growth with a plateau (Abs(toluene)=a(1-exp(-bt)) for the determination of the release rate, V (with V=a*b).
The release of toluene in static mode was determined for materials 2, 6, 7, 8, 11 and 12 doped for 25 h with toluene (see FIG. 8). These various materials possess different pore sizes and are characterized by their % of micropores (diameter<20 Å). The % of micropores is obtained by calculating the ratio between the specific surface area of adsorption by the pores with a size of less than or equal to 20 Å (micropores) and the total specific surface area of adsorption of the material (see table 1). The specific surface areas were obtained on the basis of the N.sub.2 adsorption isotherms at the temperature of liquid N.sub.2 (BET method) using cylindrical pore models and density functional theory (DFT method).
FIG. 8 collates the results of these tests in graph form. The left-hand scale corresponds to an arbitrary unit.Math.h.sup.−1, the right-hand scale to the conversion into ppm.Math.h.sup.−1. The conditions of the tests were as follows: volume of the release system=170 mL, T=293 K, optical path length of the spectrophotometer cell=1 cm, molar extinction coefficient of toluene at 203.8 nm=4890 mol.sup.−1.Math.L.Math.cm.sup.−1. Each dot corresponds to the release rate determined as described above in relation to the measurements presented in FIG. 7B.
A sharp decrease in the release rate of toluene is observed when the materials possess progressively smaller pore size distributions.
The material of example 7 was doped for 25 h in a saturation atmosphere of vapor from solid naphthalene. The release of naphthalene in static mode, the size of which is approximately twice that of toluene, from a matrix of example 7 is shown in FIG. 9, with the change in the absorbance of gaseous naphthalene as a function of time. The conditions of the tests were as follows: volume of the release system=170 mL, T=293 K, optical path length of the spectrophotometer cell=1 cm. The molar extinction coefficient of naphthalene is 135 800 mol.Math..sup.−1.Math.L.Math.cm.sup.−1 at 210 nm. This test shows that by adapting the pore size to that of the pollutant, it is also possible to modify the rate of release.
This test also shows that for a given material, less substantial doping of the naphthalene relative to the toluene is observed for a given duration of exposure to the saturation vapor of each volatile compound. The same is true of the rate of release of naphthalene in static mode (see FIG. 10), which is ˜905 times slower than that of toluene with the same material. The rate of release, expressed in h.sup.−1, was converted into ppm.Math.h.sup.−1 by taking the molar extinction coefficient of naphthalene at 210 nm (135 800 mol.Math..sup.−1.Math.L.Math.cm.sup.−1) which is given in the G.A. George et al. reference (G. A. George, G. C. Morris, The intensity of absorption of naphthalene from 30000 to 53000 cm.sup.−1, J. Mol. Spectros., 26, 67-71, (1968)).
As for toluene, the rate of release of naphthalene can be controlled according to the porosity of the material. An example is shown here with a series of experiments conducted with doping for 2 h of various materials of examples 2, 3 and 7 with the saturation vapor from solid naphthalene, with the release of the latter being monitored in static mode (see FIG. 11). These various materials possess different pore sizes and are characterized by their % of micropores (diameter <20 Å). The % of micropores is obtained by calculating the ratio between the surface area of adsorption by the pores with a size of less than or equal to 20 Å (micropores) and the total surface area of adsorption of the material (see table 1). The left-hand scale corresponds to an arbitrary unit.Math.h.sup.−1, the right-hand scale to the conversion into ppm.Math.h.sup.−1. The conditions of the tests were as follows: volume of the release system=170 mL, T=293 K, optical path length of the spectrophotometer cell=1 cm, molar extinction coefficient of naphthalene at 210 nm=135 800 mol.sup.−1.Math.L.Math.cm.sup.−1. Each dot corresponds to the release rate determined as described above relative to the measurements presented in FIG. 7B.

Release in Dynamic Mode

[0074] For the dynamic mode release tests, the material of example 4 doped for 2 h with the saturation vapor of toluene is placed in a FLEC (Field Laboratory Emission Cell) emission test cell having an internal diameter of 15 cm and a volume of 35 mL. The standardized measurement method (Standard ISO 16000-10, 2006) is based on dynamic sweeping of the surface of the doped material with a stream of wet air (RH 50±3%) and a sweep velocity of the air over the surface of the material of between 0.003 to 0.3 m.Math.s.sup.−1. In order to have a temperature of 23° C. (±1), the assembly is installed in a conditioning chamber. For measuring the amount of pollutant released, the outlet of the FLEC cell is connected to an automatic gas chromatography (GC) analyzer which is equipped with a flame ionization detector (FID). This analyzer is able to measure VOCs having between 6 and 12 carbon atoms by carrying out separation and direct analysis of the pollutants leaving the FLEC. The rate of release is then obtained via direct measurement of the concentration of pollutant released by the doped material as a function of time. FIG. 12 shows the kinetics of release of toluene as a function of time (circular dots) and the correlation of the measurement with kinetics of biexponential decay ([toluene]=a exp(-bt))+c exp(-dt)), with V1=a*b and V2=c*d.