Ultraporous sol gel monoliths

• US 7,439,272 B2
• Filed: 12/20/2004
• Issued: 10/21/2008
• Est. Priority Date: 12/20/2004
• Status: Active Grant

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Varian Incorporated (Agilent Technologies, Inc.)
• Inventors: Xu, Dengfeng
• Primary Examiner(s): Kugel; Timothy J.
• Application Number:
  US11/018,168
• Publication Number:
  US 20060131238A1
• Time in Patent Office: 1,401 Days
• Field of Search: 516/110, 516/111
• US Class Current: 516/111
• CPC Class Codes: B01D 15/26 characterised by the separation mechanism
• CPC Class Codes: B01J 20/28042 Shaped bodies; Monolithic structures
• CPC Class Codes: B01J 20/28047 Gels
• CPC Class Codes: B01J 20/28057 Surface area, e.g. B.E.T specific surface area
• CPC Class Codes: B01J 20/28069 Pore volume, e.g. total pore volume, mesopore volume, micropore volume
• CPC Class Codes: B01J 20/282 Porous sorbents ion exchange B01J39/00 - B01J41/00
• CPC Class Codes: B01J 20/286 Phases chemically bonded to a substrate, e.g. to silica or to polymers
• CPC Class Codes: B01J 20/291 Gel sorbents
• CPC Class Codes: B01J 21/08 Silica
• CPC Class Codes: B01J 2220/54 Sorbents specially adapted for analytical or investigative chromatography
• CPC Class Codes: B01J 2220/82 Shaped bodies, e.g. monoliths, plugs, tubes, continuous beds
• CPC Class Codes: B01J 35/56 Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• CPC Class Codes: C04B 2111/00793 as filters or diaphragms
• CPC Class Codes: C04B 2111/0081 as catalysts or catalyst carriers
• CPC Class Codes: C04B 2111/00836 for medical or dental applications
• CPC Class Codes: C04B 2111/00844 for electronic applications
• CPC Class Codes: C04B 35/515 based on non-oxide ceramics
• CPC Class Codes: C04B 35/553 based on fluorides
• CPC Class Codes: C04B 38/0045 by a process involving the formation of a sol or a gel, e.g. sol-gel or precipitation processes
• CPC Class Codes: C04B 38/0054 the pores being microsized or nanosized
• CPC Class Codes: C04B 38/0074 : expressed as porosity percentage

Abstract

Ultraporous sol gel monoliths and methods for preparing the same are provided, having superior flow characteristics for chromatography and analytical chemistry applications. The methods for forming an ultra porous sol-gel monolith include (a) forming a solution comprising a porogen, a matrix dissolving catalyst and a sol gel precursor; (b) allowing the solution to form a gel; and (c) drying the gel at an elevated temperature. The ultraporous sol gel monoliths are characterized by a porosity of up to about 97%, a BET surface area of at least about 50 m²/g and substantially no micropores.

Claims

1. An ultraporous sol gel monolith, wherein the sol gel monolith is characterized by having a total porosity of up to about 97% and substantially no pores with diameters less than about 2.0 nm.

2. The ultraporous sol gel monolith of claim 1, wherein the sol gel monolith is formed from a sol gel precursor selected from a metal or metalloid compound comprising Si, Ge, Sn, Al, Ga, V, Nb, Ti, Zr, or Hf, and wherein said compound is capable of undergoing a sol gel reaction to form a sol gel.

3. The ultraporous sol gel monolith of claim 2, wherein the sol gel precursor is an alkoxide or halide of silicon, germanium, aluminum, titanium, zirconium, vanadium, or hafnium, or mixtures thereof.

4. The ultraporous sol gel monolith of claim 3, wherein the sol gel precursor further comprises an organic substituent.

5. The ultraporous sol gel monolith of claim 1, wherein the sol gel monolith is characterized by a total porosity of at least about 60%.

6. The ultraporous sol gel monolith of claim 1, wherein the sol gel monolith is characterized by a BET surface area of at least about 50 m²/g.

7. The ultraporous sol gel monolith of claim 1, wherein the surface of the sol gel monolith is further modified with a silane having the formula

R¹_n—

Si—

X_4-n,

wherein R¹ is independently selected from hydrogen, C₁-C₁₀₀ substituted or unsubstituted hydrocarbyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;

wherein the substituents are selected from C₁—

C₁₂ hydrocarbyl, hydroxyl, alkoxy, halogen, amino, nitro, sulfo, cyano, glycidyl, carbamido, and carbonyl, wherein n is 0, 1, 2, or 3, and X is a leaving group.

8. A method for forming an ultraporous sol-gel monolith lacking pores with diameters less than about 2.0 nm comprising

(a) forming an aqueous solution comprising a porogen, a catalyst comprising a matrix dissolving agent and a sol gel precursor;

(b) allowing the solution to form a gel; and

(c) drying the gel at an elevated temperature.

9. The method of claim 8, wherein the matrix dissolving agent is selected from hydrofluoric acid or a hydrofluoric acid source.

10. The method of claim 9, wherein the hydrofluoric acid source is selected from F₂(g), fluorides of Group I elements;

fluorides of Group II elements;

fluorides of Group III elements;

fluorides of Group IV elements;

fluorides of group V elements;

fluorides of Group VI elements;

or fluoride salts.

11. The method of claim 10, wherein said hydrofluoric acid source is selected from F₂(g), KHF₂, BF₃, SiF₄, GeF₄, NF₃, PF₃, PF₅, PF₃Cl₂, SF₄, SF₆, NH₄HF₂, a fluorosilane, a fluorogermane, or mixtures thereof.

12. The method of claim 9, wherein the hydrofluoric acid is present at a molar ratio of up to 1 mole HF per mole of the sol-gel precursor.

13. The method of claim 8, further comprising

(d) calcining the gel at a temperature of at least 400°

C.

14. The method of claim 13, wherein the drying and calcining steps are performed at the same time.

15. The ultraporous sol gel monolith produced by the method of claim 13.

16. The method of claim 8, wherein the sol gel precursor is an alkoxide or halide of silicon, germanium, aluminum, titanium, zirconium, vanadium, or hafnium, or mixtures thereof.

17. The method of claim 8, wherein steps (a) and (b) are performed at a temperature between the solution freezing point temperature and the solution boiling temperature.

18. The method of claim 8, wherein the step (c) is performed at a temperature of up to about 400°

C.

19. The method of claim 8, wherein the porogen is a hydrophilic polymer or a surfactant.

20. The method of claim 8, further comprising modifying the ultraporous sol gel monolith with a bonded phase.

21. The method of claim 8, wherein the sol gel monolith is modified with a silane having the formula

R¹_n—

Si—

X_4-n,

wherein R¹ is independently selected from hydrogen, C₁-C₁₀₀ substituted or unsubstituted hydrocarbyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl;

wherein the substituents are selected from C₁-C₁₂ hydrocarbyl, hydroxyl, alkoxy, halogen, amino, nitro, sulfo, cyano, glycidyl, carbamido, and carbonyl, wherein n is 0, 1, 2, or 3, and X is a leaving group.