A method of producing a silica gel by hydrolyzing a silicon alkoxide and subjecting the resulting hydrogel to a hydrothermal treatment substantially without aging it is described. Also described in a silica gel produced by such a method and a silica gel which has the following characteristics: (a) the pore volume is from 0.6 to 1.6 ml/g, (b) the specific surface area is from 300 to 900 m 2 /g, (c) the mode diameter (Dmax) of pores is less than 20 nm, (d) the volume of pores having diameters within ±20% of Dmax is at least 50% of the total pore volume, (e) it is amorphous, and (f) the content of metal impurities is at most 500 ppm.
1. A method of producing a silica gel, which comprises:
hydrolyzing a silicon alkoxide, thereby forming a hydrogel; and
subjecting the hydrogel to a hydrothermal treatment substantially without aging the hydrogel, thereby producing said silica gel having the following characteristics:
(a) a pore volume ranging from 0 6 to 1.6 ml/g,
(b) a specific surface area ranging from 300 to 900 m 2 /g,
(c) a mode diameter (Dmax) of pores of less than 20 nm,
(d) a volume of pores having diameters within ±20% of Dmax of at least 50% of the total pore volume;
(e) it is amorphous, and
(f) the content of metal impurities is at most 500 ppm.
2. The method for producing a silica gel according to claim 1 , wherein a hydrogel having a breaking stress of at most 6 MPa is subjected to the hydrothermal treatment.
3. The method for producing a silica gel according to claim 1 , wherein the hydrothermal treatment is carried out at a temperature ranging from 50 to 150° C. for from 1 to 10 hours.
4. The method for producing a silica gel according to claim 1 , wherein an ammonia water is used for the hydrothermal treatment is conducted in ammonia water.
5. The method for producing a silica gel according to claim 1 , wherein hydrolysis of said silicon alkoxide is conducted in the absence of a template.
6. A silica gel, produced by a process comprising:
hydrolyzing a silicon alkoxide, thereby forming a hydrogel; and
subjecting the hydrogel to a hydrothermal treatment substantially without aging the hydrogel, thereby producing said silica gel having the following characteristic:
(a) a pore volume ranging from 0.6 to 1.6 ml/g,
(b) a specific surface area ranging from 300 to 900 m 2 /g,
(c) a mode diameter (Dmax) of pores of less than 20 nm,
(d) a volume of pores having diameters within ±20% of Dmax of at least 50% of the total pore volume;
(e) it is amorphous, and
(f) the content of metal impurities is at most 500 ppm.
7. The silica gel according to claim 6 , wherein a hydrogel having a breaking stress of at most 6 MPa is subjected to the hydrothermal treatment.
8. The silica gel according to claim 6 , wherein the hydrothermal treatment is carried out at a temperature ranging from 50 to 150° C. for from 1 to 10 hours.
9. The silica gel according to claim 6 , wherein the hydrothermal treatment is conducted in ammonia water.
10. The silica gel according to claim 6 , wherein the pore volume ranges from 0.8 to 1.6 ml/g.
11. The silica gel according to claim 6 , wherein the specific surface area ranges from 400 to 900 m 2 /g.
12. The silica gel according to claim 6 , wherein the mode diameter (Dmax) is at least 2 nm.
13. The silica gel according to claim 6 , wherein the volume of pores having diameters within ±20% of Dmax is at least 60% of the total pore volume.
14. The silica gel according to claim 6 , wherein the content of metal impurities is at most 10 ppm.
15. The silica gel according to claim 14 , wherein the content of metal impurities is at most 1 ppm.
16. The silica gel according to claim 6 , wherein the differential pore volume at the mode diameter (Dmax) ranges from 5.0 to 12.0 ml/g.
17. The silica gel according to claim 6 , wherein the value of Q4/Q3 in solid state Si-NMR is at least 1.3.
18. The silica gel according to claim 6 , wherein hydrolysis of said silicon alkoxide is conducted in the absence of a template.
19. The silica gel according to claim 6 , wherein hydrolysis of said silicon alkoxide is conducted in the absence of a template.
20. A silica gel which has the following characteristics:
(a) a pore volume ranging from 0.6 to 1.6 ml/g,
(b) a specific surface area ranging from 300 to 900 m 2 /g,
(c) a mode diameter (Dmax) of pores of less than 20 nm,
(d) a volume of pores having diameters within ±20% of Dmax of at least 50% of the total pore volume;
(e) it is amorphous, and
(f) the content of metal impurities is at most 500 ppm.
21. The silica gel according to claim 20 , wherein the pore volume ranges from 0.8 to 1.6 ml/g.
22. The silica gel according to claim 20 , wherein the specific surface area ranges from 400 to 900 m 2 /g.
23. The silica gel according to claim 20 , wherein the mode diameter (Dmax) is at least 2 nm.
24 .The silica gel according to claim 20 , wherein the volume of pores having diameters within ±20% of Dmax is at least 60% of the total pore volume.
25. The silica gel according to claim 20 , wherein the content of metal impurities is at most 10 ppm.
26. The silica gel according to claim 25 , wherein the content of metal impurities is at most 1 ppm.
27. The silica gel according to claim 20 , wherein the differential pore volume at the mode diameter (Dmax) ranges from 5.0 to 12.0 ml/g.
28. The silica gel according to claim 20 , wherein th value of Q4/Q3 in solid state Si-NMR is at least 1.3.
29. The silica gel according to claim 20 , which is produced by means of a step of hydrolyzing a silicon alkoxide.
30. A method of producing a silica gel, which comprises:
hydrolyzing a silicon alkoxide, thereby forming a hydrogel which has breaking stress of at most 6 MPa; and
subjecting the hydrogel to a hydrothermal treatment substantially without aging the hydrogel, thereby producing said silica gel having the following characteristics:
(a) a pore volume ranging from 0.6 to 1.6 ml/g,
(b) a specific surface area ranging from 300 to 900 m 2 /g,
(c) a mode diameter (Dmax) of pores of less than 20 nm,
(d) a volume of pores having diameters within ±20% of Dmax of at least 50% of the total pore volume;
(e) it is amorphous, and
(f) the content of metal impurities is at most 500 ppm.