Method for preparation of silica particles

Claim 2

A process for the preparation of substantially spherical silica particles, comprising the steps of: 1) preparing at least one acid aqueous silica sol with an alkali metal content below 100 ppm and a particle size essentially below 3 nm; 2) heat treating the prepared sol in an ammonium or amine basic solution resulting in growth of the sol particles to a size corresponding to an area within the range of from about 50 to about 500 m 2 /g; 3) emulsifying the sol, after optional concentration, in an organic medium which is not miscible with water, or has a limited miscibility or solubility with water, and in the presence of a surface active agent; 4) gelling the formed sol drops by dewatering at a temperature of from about 30° C. to about 100° C. and at a pH of from about 5 to about 9; 5) heat treating the produced gel particles for removal of substantially all organic material; and 6) post-treating the gel particles in a basic environment containing ammonium or an amine.

Claim 3

A process according to claim 1, characterized in that gelling is carried out in the presence of a substance which accelerates the gelling.

Claim 4

A process according to claim 1, characterized in that ammonium hydroxide solution is used in steps 2) and 6).

Claim 5

A process according to claim 1, characterized in that the sol which is emulsified is polydisperse.

Claim 6

A process according to claim 1, characterized in that the heat treatment of the gel particles is carried out at a temperature of at least 600° C.

Claim 7

A process according to claim 1, characterized in that the post-treatment in the ammonium or amine basic environment is carried out at a pH of at least about 11.3.

Claim 8

A process for the preparation of silica particles, comprising the steps of: 1) preparing at least one acid aqueous silica sol with an alkali metal content below 100 ppm and a particle size essentially below 3 nm; 2) heat treating the prepared sol in an ammonium or amine basic solution resulting in growth of the sol particles to a size corresponding to an area within the range of from about 50 to about 500 m 2 /g; 3) emulsifying the sol, after optional concentration, in an organic medium which is not miscible with water, or has a limited miscibility or solubility with water, and in the presence of a surface active agent; 4) gelling the formed sol drops by dewatering at a temperature of from about 30° C. to about 100° C. and at a pH of from about 5 to about 9; 5) heat treating the produced gel particles for removal of substantially all organic material; and 6) post-treating the gel particles in a basic environment containing ammonium or an amine; wherein the silica particles are substantially spherical and have a particle size within the range of from about 1 to about 100 μm, a pore size distribution where the part of the pore volume within the range of from 0.5d to 1.5d, where d is the mean pore diameter, is greater than 90% and an alkali metal content below 100 ppm.

Claim 9

A process for the preparation of silica particles, comprising the steps of: 1) preparing at least one acid aqueous silica sol with an alkali metal content below 100 ppm and a particle size essentially below 3 nm; 2) heat treating the prepared sol in an ammonium or amine basic solution resulting in growth of the sol particles to a size corresponding to an area within the range of from about 50 to about 500 m 2 /g; 3) emulsifying the sol, after optional concentration, in an organic medium which is not miscible with water, or has a limited miscibility or solubility with water, and in the presence of a surface active agent; 4) gelling the formed sol drops by dewatering at a temperature of from about 30° C. to about 100° C. and at a pH of from about 5 to about 9; 5) heat treating the produced gel particles for removal of substantially all organic material; and 6) post-treating the gel particles in a basic environment containing ammonium or an amine; wherein the silica particles are substantially spherical and have a particle size within the range of from about 1 to about 100 μm, a pore size distribution where the part of the pore volume within the range of from 0.5d to 1.5d, where d is the mean pore diameter, is greater than 90% and an alkali metal content below 100 ppm.

Claim 10

A process according to claim 7, wherein gelling is carried out in the presence of a substance which accelerates the gelling.

Claim 11

A process according to claim 7, wherein ammonium hydroxide solution is used in steps 2) and 6).

Claim 12

A process according to claim 7, wherein the sol which is emulsified is polydisperse.

Claim 13

A process according to claim 7, wherein the heat treatment of the gel particles is carried out at a temperature of at least 600° C.

Claim 14

A process according to claim 7, wherein the post-treatment in the ammonium or amine basic environment is carried out at a pH of at least about 11.3.