Silica-containing porous bodies of controlled pore size

Claim 1

A method for making porous silica-containing articles exhibiting compressive strengths in the pristine state greater than about 50 psi, having pore diameters ranging between about 100A-1 micron, wherein at least 80% of the pores therein fall within ±30% of the average pore diameter value, which consists of (a) preparing solutions having a pH between 10-15 and containing about 1-12 moles SiO 2 /liter in solution from silicate solutions selected from the group consisting of lithium polysilicate, sodium silicate, potassium silicate, quaternary ammonium silicate, and colloidal silica; (b) combining those solutions in one of the indicated proper proportions equivalent to: (A) a weight ratio of 19:1 to 1:4 potassium silicate solution to colloidal silica solution wherein said potassium silicate solution consists essentially of 8.3% K 2 O, 20.8% SiO 2 , balance H 2 O and said colloidal silica solution consists essentially of 40% SiO 2 , balance H 2 O; (b) a weight ratio of 1:9 to 1:3 sodium silicate solution to colloidal silica solution wherein said sodium silicate solution consists essentially of 6.8% Na 2 O, 25.3% SiO 2 , balance H 2 O and the colloidal silica solution is that defined in (A); (c) a weight ratio of 9:1 to 1:4 potassium silicate solution and/or sodium silicate solution to quaternary ammonium silicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said quaternary ammonium silicate solution consists essentially of 9.9% quaternary ammonium ions, 45% SiO 2 , balance H 2 O; (d) a weight ratio of 19:1 to 1:4 potassium silicate solution and/or sodium silicate solution to lithium polysilicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said lithium polysilicate solution consists essentially of 2.1% Li 2 O, 20% SiO 2 , balance H 2 O; (c) reacting an organic compound therewith selected from the group consisting of formaldehyde, paraformaldehyde, formamide, glyoxal, methyl formate, ethyl formate, methyl acetate, ethyl acetate, and mixtures thereof at a temperature between the freezing point and the boiling point of the solution for a sufficient period of time to polymerize the silica into a coherent, porous gelled body; and (d) leaching said gelled body with a weak acid solution to remove excess alkali metal oxide.

Claim 2

A method for making porous silica-containing articles exhibiting compressive strengths in the pristine state greater than about 50 psi, having pore diameters ranging between about 100A-1 micron, wherein at least 80% of the pores therein fall within ±30% of the average pore diameter value, which consists of (a) preparing solutions having a pH between 10-15 and containing about 1-12 moles SiO 2 /liter in solution from silicate solutions selected from the group consisting of lithium polysilicate, sodium silicate, potassium silicate, quaternary ammonium silicate, and colloidal silica; (b) combining those solutions in one of the indicated proper proportions equivalent to: (A) a weight ratio of 19:1 to 1:4 potassium silicate solution to colloidal silica solution wherein said potassium silicate solution consists essentially of 8.3% K 2 O, 20.8% SiO 2 , balance H 2 O and said colloidal silica solution consists essentially of 40% SiO 2 , balance H 2 O; (b) a weight ratio of 1:9 to 1:3 sodium silicate solution to colloidal silica solution wherein said sodium silicate solution consists essentially of 6.8% Na 2 O, 25.3% SiO 2 , balance H 2 O and the colloidal silica solution is that defined in (A); (c) a weight ratio of 9:1 to 1:4 potassium silicate solution and/or sodium silicate solution to quaternary ammonium silicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said quaternary ammonium silicate solution consists essentially of 9.9% quaternary ammonium ions, 45% SiO 2 , balance H 2 O; (d) a weight ratio of 19:1 to 1:4 potassium silicate solution and/or sodium silicate solution to lithium polysilicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said lithium polysilicate solution consists essentially of 2.1% Li 2 O, 20% SiO 2 , balance H 2 O; (c) reacting an organic compound therewith selected from the group consisting of formaldehyde, paraformaldehyde, formamide, glyoxal, methyl formate, ethyl formate, methyl acetate, ethyl acetate, and mixtures thereof at a temperature between the freezing point and the boiling point of the solution for a sufficient period of time to polymerize the silica into a coherent, porous gelled body; and (d) leaching said gelled body with a weak acid solution to remove excess alkali metal oxide.

Claim 6

A method for making silica-containing articles of bimodal porosity exhibiting compressive strengths in the pristine state greater than about 50 psi, having pore diameters ranging between about 100A-1 micron, and wherein at least 80% of the pores in each level of porosity fall within ±30% of the average pore diameter of that level, which consists of (a) preparing solutions having a pH between 10-15 and containing about 1-12 moles SiO 2 /liter in solution from silicate solutions selected from the group consisting of lithium polysilicate, sodium silicate, potassium silicate, quaternary ammonium silicate, and colloidal silica; (b) combining those solutions in one of the indicated proper proportions equivalent to: (A) a weight ratio of 19:1 to 1:4 potassium silicate solution to colloidal silica solution wherein said potassium silicate solution consists essentially of 8.3% K 2 O, 20.8% SiO 2 , balance H 2 O and said colloidal silica solution consists essentially of 40% SiO 2 , balance H 2 O; (b) a weight ratio of 1:9 to 1:3 sodium silicate solution to colloidal silica solution wherein said sodium silicate solution consists essentially of 6.8% Na 2 O, 25.3% SiO 2 , balance H 2 O and the colloidal silica solution is that defined in (A); (c) a weight ratio of 9:1 to 1:4 potassium silicate solution and/or sodium silicate solution to quaternary ammonium silicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said quaternary ammonium silicate solution consists essentially of 9.9% quaternary ammonium ions, 45% SiO 2 , balance H 2 O; (d) a weight ratio of 19:1 to 1:4 potassium silicate solution and/or sodium silicate solution to lithium polysilicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said lithium polysilicate solution consists essentially of 2.1% Li 2 O, 20% SiO 2 , balance H 2 O; (c) admixing up to 70% by weight of particulate materials of uniform size having a diameter less than about 1 micron, which can be burned out at a temperature below that at which the silica body will sinter or melt substantially, and which are undissolved in and/or unreactive with said silicate solutions and/or organic compounds recited in (d) below; (d) reacting an organic compound therewith selected from the group consisting of formaldehyde, paraformaldehyde, formamide, glyoxal, methyl formate, ethyl formate, methyl acetate, ethyl acetate, and mixtures thereof at a temperature between the freezing point and the boiling point of the solution for a sufficient period of time to polymerize the silica into a coherent, porous gelled body; (e) leaching said gelled body with a weak acid solution to remove excess alkali metal oxides; and (f) firing said leached body at a temperature sufficiently high to burn out said particulate materials but below the sintering or melting temperature of the silica body.

Claim 7

A method for making silica-containing articles of bimodal porosity exhibiting compressive strengths in the pristine state greater than about 50 psi, having pore diameters ranging between about 100A-1 micron, and wherein at least 80% of the pores in each level of porosity fall within ±30% of the average pore diameter of that level, which consists of (a) preparing solutions having a pH between 10-15 and containing about 1-12 moles SiO 2 /liter in solution from silicate solutions selected from the group consisting of lithium polysilicate, sodium silicate, potassium silicate, quaternary ammonium silicate, and colloidal silica; (b) combining those solutions in one of the indicated proper proportions equivalent to: (A) a weight ratio of 19:1 to 1:4 potassium silicate solution to colloidal silica solution wherein said potassium silicate solution consists essentially of 8.3% K 2 O, 20.8% SiO 2 , balance H 2 O and said colloidal silica solution consists essentially of 40% SiO 2 , balance H 2 O; (b) a weight ratio of 1:9 to 1:3 sodium silicate solution to colloidal silica solution wherein said sodium silicate solution consists essentially of 6.8% Na 2 O, 25.3% SiO 2 , balance H 2 O and the colloidal silica solution is that defined in (A); (c) a weight ratio of 9:1 to 1:4 potassium silicate solution and/or sodium silicate solution to quaternary ammonium silicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said quaternary ammonium silicate solution consists essentially of 9.9% quaternary ammonium ions, 45% SiO 2 , balance H 2 O; (d) a weight ratio of 19:1 to 1:4 potassium silicate solution and/or sodium silicate solution to lithium polysilicate solution wherein said potassium silicate solution is that defined in (A), said sodium silicate solution is that defined in (B), and said lithium polysilicate solution consists essentially of 2.1% Li 2 O, 20% SiO 2 , balance H 2 O; (c) admixing up to 70% by weight of particulate materials of uniform size having a diameter less than about 1 micron, which can be burned out at a temperature below that at which the silica body will sinter or melt substantially, and which are undissolved in and/or unreactive with said silicate solutions and/or organic compounds recited in (d) below; (d) reacting an organic compound therewith selected from the group consisting of formaldehyde, paraformaldehyde, formamide, glyoxal, methyl formate, ethyl formate, methyl acetate, ethyl acetate, and mixtures thereof at a temperature between the freezing point and the boiling point of the solution for a sufficient period of time to polymerize the silica into a coherent, porous gelled body; (e) leaching said gelled body with a weak acid solution to remove excess alkali metal oxides; and (f) firing said leached body at a temperature sufficiently high to burn out said particulate materials but below the sintering or melting temperature of the silica body.