Process for producing isocyanate-based xerogels and aerogels with mineral acids

Abstract

The present invention is directed to a process for preparing a porous material, at least compris-ing the steps of providing a mixture (I) comprising a composition (A) at least comprising at least one polyfunctional isocyanate as component (ai) and at least one mineral acid (aa), and a sol-vent (B), reacting the components in the composition (A) obtaining an organic gel, and drying of the gel obtained. The invention further relates to the porous materials which can be obtained in this way and the use of the porous materials as thermal insulation material and as catalysts.

Claims

1. A process for preparing a porous material, comprising: a) providing a mixture (I) comprising (i) a composition (A) comprising at least one polyfunctional isocyanate as component (ai), and at least one mineral acid (aa) and (ii) a solvent (B), b) reacting the components in the composition (A) to obtain an organic gel, and c) drying the obtained gel, wherein the mineral acid (aa) is selected from the group consisting of mineral oxo-acids comprising sulphur, boron, nitrogen, phosphorus, silicon, chlorine, bromine, iodine, fluorine, chromium, vanadium, manganese, rhenium, technetium, arsenic, selenium and tellurium.

2. The process according to claim 1, wherein the composition (A) comprises amines in an amount in a range of from 0 to 2 wt. %, alcohols in an amount in a range of from 0 to 20 wt. %, and water in an amount in a range of from 0 to 1 wt. %.

3. The process according to claim 1, wherein the polyfunctional isocyanate is selected from the group consisting of aromatic, aliphatic, cycloaliphatic and araliphatic isocyanates.

4. The process according to claim 1, wherein the composition (A) comprises the component (ai) in an amount in a range from 40 to 99 mol %.

5. The process according to claim 1, wherein the composition (A) comprises the mineral acid (aa) in an amount in a range of from 60 to 1 mol %.

6. The process according to claim 1, wherein the solvent (B) is replaced by a solvent (S) after the organic gel is obtained and before drying of the gel in c).

7. The process according to claim 1, wherein the drying in c) comprises converting a liquid in the gel into a gaseous state at a temperature and a pressure below a critical temperature and a critical pressure of the liquid in the gel.

8. A porous material, which is obtained by the process according to claim 1.

9. A thermal insulation material comprising the porous material of claim 8.

10. The porous materials according to claim 8, wherein the porous material is a catalyst.

Description

EXAMPLES

(1) 1. Materials

(2) Desmodur RE: Solution of approx. 27% triphenylmethane-4,4,4-triisocyanate (TIPM) in ethyl acetate having an NCO content of 9.30.2% in accordance with M105-ISO 11909 a functionality in the region of three and a viscosity of 3 mPa.Math.s at 20 C. in accordance with DIN 53 015.

(3) 2. Methods

(4) 2.1 Physical Characterization

(5) Bulk densities (b) were calculated from the weight and the physical dimensions of the samples. Skeletal densities (s) were determined with helium pycnometry using a Micromeritics AccuPyc II 1340 instrument.

(6) 2.2 Structural Characterization

(7) BET surface areas and pore size distributions for pore sizes in the 1.7-300 nm range were determined with N.sub.2-sorption porosimetry at 77 K using a Micromeritics ASAP 2020 surface area and porosity analyzer. Micropore analysis was conducted with CO.sub.2-sorption up to 760 torr (relative pressure of 0.03) at 0 C. using a Micromeritics Tristar II 3020 version 3.02.

(8) 3. Preparation of Porous Materials Using H.sub.3BO.sub.3

(9) 3.1 Preferred Procedure for Producing the Porous Materials BPUA-x:

(10) In a typical procedure, H.sub.3BO.sub.3 (0.61 g, 0.01 mol) was dissolved in anhydrous DMF and the solution was added to 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM). The resulting sol was stirred at room temperature under N.sub.2 for 15 min, and was poured into molds (Wheaton 4 mL Polypropylene Omni-Vials 1.04 cm in inner diameter, Fisher part No. 225402), which were then sealed and left for gelation. The total weight percent concentration of monomers (TIPM+H.sub.3BO.sub.3) in the sol was varied by varying the amount of solvent (DMF), and is denoted by extension -x in the sample names. Gelation of BPUA-x took place at room temperature. All formulations and gelation times are summarized in Table 1. Gels were aged for 12 h at room temperature in their molds, removed from the molds, washed with DMF (2) and acetone (4, using 4 the volume of the gel for each wash), and were dried in an autoclave with liquid CO.sub.2 extracted as a supercritical fluid (SCF).

(11) 3.2 Preferred Procedure for Producing the Porous Materials PUA-y:

(12) In a typical procedure, Et3N was added at 0.3% w/w relative to the mass of a solution of 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM), H.sub.2O (0.54 g, 0.03 mol) and anhydrous DMF. The resulting sol was stirred at room temperature under N.sub.2 for 10 min, and was poured into molds (Wheaton 4 mL Polypropylene Omni-Vials 1.04 cm in inner diameter, Fisher part No. 225402), which were sealed and left for gelation at room temperature. The total weight percent concentration of monomers (TIPM+H.sub.2O) in the sol was varied by varying the amount of solvent (DMF), and is denoted by extension -y in the sample names. All formulations and gelation times are summarized in Table. Gels were aged for 12 h at room temperature in their molds. Subsequently, gels were removed from the molds, washed with DMF (2), acetone (4, using 4 the volume of the gel for each wash), and were dried in an autoclave with liquid CO.sub.2 extracted as a SCF.

(13) 3.3 Drying

(14) Drying of wet-gels with supercritical fluid (SCF) CO.sub.2 was carried out in an autoclave (SPIDRY Jumbo Supercritical Point Dryer, SPI Supplies, Inc. West Chester, Pa. or a SpeedSFE system, Applied Separations, Allentown, Pa.). Samples were loaded into the autoclave and acetone was added till all samples were submerged. The pressure vessel was closed and liquid CO.sub.2 was allowed in at room temperature until it displaced all acetone, which was drained out. Liquid CO.sub.2 was allowed in the vessel several more times until all acetone was extracted out of the pores of the samples. At that point, CO.sub.2 started coming out forming dry ice. Subsequently, the temperature of the autoclave was raised to 40 C. and SCF CO.sub.2 was vented off as a gas.

(15) TABLE-US-00001 TABLE 1 Formulations of BPUA-x aerogels. Boric acid Desmodur RE .sup.b TIPM DMF mass volume .sup.a C volume mass mass .sup.c C mass volume Sample (g) (mL) mmol (M) (mL) (g) (g) mmol (M) (g) (mL) BPUA-1 0.062 0.043 1.0 0.089 1.33 1.359 0.367 1.0 0.089 9.30 9.79 BPUA-2 0.062 0.043 1.0 0.181 1.33 1.359 0.367 1.0 0.181 3.94 4.14 BPUA-3 0.062 0.043 1.0 0.275 1.33 1.359 0.367 1.0 0.275 2.15 2.26 BPUA-4 0.062 0.043 1.0 0.371 1.33 1.359 0.367 1.0 0.371 1.26 1.32 .sup.a The volume of boric acid was calculated based on its density: 1.43 g cm.sup.3. .sup.b The mass of commercial Desmodur RE was calculated based on its density as measured in our lab (1.022 g cm.sup.3). .sup.c The mass of TIPM in Desmodur RE was calculated based on the 27% w/w concentration given by the supplier.

(16) TABLE-US-00002 TABLE 2 Formulations of PUA-y aerogels. Desmodur RE .sup.a TIPM H.sub.2O .sup.c DMF Et.sub.3N .sup.d volume mass mass .sup.b C volume mass mass volume volume mass w/w Sample (mL) (g) (g) mmol (M) (mL) (g) mmol (g) (mL) (mL) (g) (%) PUA-1 1.33 1.359 0.367 1.0 0.103 0.05 0.05 3.0 7.81 8.22 0.041 0.030 0.3 PUA-2 1.33 1.359 0.367 1.0 0.208 0.05 0.05 3.0 3.22 3.39 0.022 0.016 0.3 PUA-3 1.33 1.359 0.367 1.0 0.314 0.05 0.05 3.0 1.69 1.78 0.016 0.012 0.3 PUA-4 1.33 1.359 0.367 1.0 0.422 0.05 0.05 3.0 0.93 0.98 0.009 0.007 0.3 .sup.a The mass of commercial Desmodur RE was calculated based its density as measured in our lab (1.022 g cm.sup.3). .sup.b The mass of TIPM in Desmodur RE was calculated based on the 27% w/w concentration given by the supplier. .sup.d The amount of the catalyst (Et.sub.3N) was varied so that its concentration remained constant at 0.3% w/w relative to the sol (Desmodur RE + H.sub.2O + DMF). .sup.c The amount of H.sub.2O was set at a stoichiometric amount to the NCO groups of TIPM, namely at 3 mol equivalents relative to TIPM.

(17) TABLE-US-00003 TABLE 3 Material characteristics of BPUA-x and PUA-y aerogels. average BET pore sample linear skeletal specific pore volume surface diameter I.D. shrinkage bulk density, density, (cm.sup.3 g.sup.1) area, (nm) x or y (%) .sup.a,b .sub.b (g cm.sup.3) .sup.a .sub.s (g cm.sup.3) .sup.c V.sub.Total .sup.d V.sub.1.7-300.sub..sub.nm .sub.e V.sub.<7.97.sub..sub. .sup.f (m.sup.2 g.sup.1) BJH .sup.g BPUA-x 1 52.34 0.61 0.283 0.008 1.254 0.001 2.74 1.97 0.047 367 42(21) 2 50.13 0.20 0.467 0.004 1.249 0.002 1.34 1.27 0.033 398 34(16) 3 47.19 0.03 0.545 0.004 1.242 0.002 1.03 0.74 0.036 340 14(10) 4 41.54 0.14 0.576 0.005 1.251 0.002 0.93 0.78 0.035 317 17(9) PUA-y 1 54.10 1.00 0.393 0.033 1.231 0.005 1.73 1.35 0.024 278 27(17) 2 48.96 0.40 0.600 0.018 1.252 0.001 0.86 0.68 0.039 291 11(14) 3 40.45 0.48 0.557 0.027 1.253 0.001 0.99 0.76 0.029 327 10(13) 4 30.76 0.41 0.428 0.003 1.233 0.003 1.52 1.02 0.034 353 16(12) .sup.a Average of 3 samples. .sup.b Linear shrinkage = 100(mold diameter sample diameter)/(mold diameter). .sup.c Single sample, average of 50 measurements. .sup.d Calculated via VTotal = (1/b) (1/s). .sub.e Cumulative volume of pores between 1.7 nm and 300 nm from N2-sorption data and the BJH desorption method. .sup.f Total pore volume of pores less than 7.97 from CO2 sorption data at 273K using the single-point absorption method at P/Po = 0.03. .sup.g From the BJH plots: first numbers are peak maxima; numbers in (parentheses) are full widths at half maxima.

(18) TABLE-US-00004 TABLE 4 Formulations of other Acid-PUA aerogels. Mineral Mineral acid Desmodur RE .sup.b TIPM Solvent .sup.d acid mass volume .sup.a C volume mass mass .sup.c C mass volume used (g) (mL) mmol (M) (mL) (g) (g) mmol (M) (g) (mL) H.sub.3PO.sub.4 0.098 0.051 1.00 0.371 1.33 1.359 0.367 1.00 0.371 1.45 1.31 H.sub.3PO.sub.3 0.123 0.074 1.50 0.529 1.33 1.359 0.367 1.00 0.352 1.58 1.43 H.sub.2SeO.sub.3 0.193 0.064 1.50 0.436 1.33 1.359 0.367 1.00 0.290 1.94 2.05 Te(OH).sub.6 0.114 0.037 0.50 0.168 1.33 1.359 0.367 1.00 0.336 1.53 1.61 H.sub.5IO.sub.6 0.136 0.097 0.60 0.190 1.33 1.359 0.367 1.00 0.316 1.64 1.73 H.sub.3AuO.sub.3 0.248 0.023 1.00 0.079 1.33 1.359 0.367 1.00 0.079 10.69 11.25 .sup.a The volume of boric acid was calculated based on its density: 1.43 g cm.sup.3. .sup.b The mass of commercial Desmodur RE was calculated based on its density as measured in our lab (1.022 g cm.sup.3). .sup.c The mass of TIPM in Desmodur RE was calculated based on the 27% w/w concentration given by the supplier.
4. Preparation of Porous Materials Using Other Mineral Acids
4.1 General Procedure

(19) Phosphoric acid (pure), was purchased from Acros Organics, phosphorous acid (98%) was purchased from Alfa Aesar, telluric acid (99%), selenous acid (98%), periodic acid (99%) and auric acid were purchased from Sigma-Aldrich. All sols were formulated so that the weight percent of monomers (TIPM+mineral acid) was kept constant at 16%. All formulations and gelation times are summarized in Table S.9. Materials characterization data are provided in Table S.10. Specifically:

(20) 4.2 Gelation of TIPM and H.sub.3PO.sub.4:

(21) H.sub.3PO.sub.4 (0.98 g, 0.010 mol) was dissolved in anhydrous DMSO (13.1 mL, 14.5 g) and the solution was cooled in a dry ice/acetone bath (78 C.). As that solution thawed, it was added to cold (78 C.) 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(22) 4.3 Gelation of TIPM and H.sub.3PO.sub.3:

(23) H.sub.3PO.sub.3 (1.23 g, 0.015 mol) was dissolved in anhydrous DMSO (14.3 mL, 15.8 g) and the solution was cooled in a dry ice/acetone bath (78 C.). As that solution thawed, it was added to cold (78 C.) 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(24) 4.4 Gelation of TIPM and H.sub.2SeO.sub.3:

(25) H.sub.2SeO.sub.3 (1.93 g, 0.015 mol) was dissolved in anhydrous DMF (20.5 mL, 19.4 g), and the solution was cooled in a dry ice/acetone bath (78 C.). The cold solution was added to cold (78 C.) 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(26) 4.5 Gelation of TIPM and Te(OH).sub.8:

(27) Te(OH).sub.6 (1.14 g, 0.005 mol) was dissolved in anhydrous DMF (16.1 mL, 15.3 g), the solution was added at room temperature to 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(28) 4.6 Gelation of TIPM and H.sub.5IO.sub.5:

(29) H.sub.5IO.sub.6 (1.36 g, 0.006 mol) was dissolved in anhydrous DMF (17.3 mL, 16.4 g), and the solution was added at room temperature to 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(30) 4.7 Gelation of TIPM and H.sub.3AuO.sub.3:

(31) H.sub.3AuO.sub.3 (2.48 g, 0.01 mol) was dissolved in anhydrous DMF (112.5 mL, 106.9 g), and the solution was added at room temperature to 13.6 g of Desmodur RE (containing 3.67 g, 0.01 mol of TIPM) and the mixture was stirred vigorously.

(32) The resulting sols were poured in molds and were left at room temperature to gel, except the H.sub.3AuO.sub.3 sols, which were placed in an oven at 90 C. After aging (12 h at room temperature, except the H.sub.3AuO.sub.3 gels, which were aged at 90 C.) gels were removed from the molds, were washed with DMF (2), acetone (4, using 4 the volume of the gel for each wash) and were dried in an autoclave with liquid CO.sub.2 taken out at the end as a supercritical fluid (SCF).

(33) TABLE-US-00005 TABLE 5 Material characteristics of other Acid-PUA aerogels specific pore volume av. pore linear skeletal (cm.sup.3 g.sup.1) BET surf. diameter, Mineral shrinkage bulk density, density, V.sub.Total .sup.e V.sub.1.7-300 nm .sup.f V.sub.Total/ area, (nm) acid used (%) .sup.a,b .sub.b (g cm.sup.3) .sup.a .sub.s (g cm.sup.3) .sup.c V.sub.1.7-300 nm (m.sup.2 g.sup.1) BJH .sup.h H.sub.3PO.sub.4 30.3 0.2 0.41 0.03 1.40 0.01 1.71 1.29 1.32 218 27.5 H.sub.3PO.sub.3 39.1 0.5 0.55 0.01 1.40 0.01 1.11 0.92 1.21 298 13.3 H.sub.2SeO.sub.3 39.7 0.5 0.21 0.03 1.85 0.06 4.33 0.04 108 17 11.1 Te(OH).sub.6 44.7 0.4 0.63 0.03 1.83 0.06 1.03 0.78 1.32 335 12.3 H.sub.5IO.sub.6 45.2 0.8 0.78 0.03 1.60 0.01 0.65 0.60 1.08 330 7.44 H.sub.3AuO.sub.3 55.4 0.6 0.32 0.04 2.38 0.05 2.695 0.571 4.71 177 7.4 .sup.a Average of 3 samples. .sup.b Linear shrinkage = 100(mold diameter sample diameter)/(mold diameter). .sup.c Single sample, average of 50 measurements. .sup.d Calculated via VTotal = (1/b)-(1/s). .sup.e Cumulative volume of pores between 1.7 nm and 300 nm from N2-sorption data and the BJH desorption method. .sup.f Total pore volume of pores less than 7.97 from CO2 sorption data at 273K using the single-point absorption method at P/Po = 0.03. .sup.g From the BJH plots: first numbers are peak maxima; numbers in (parentheses) are full widths at half maxima.