Photocatalyst with modified alkyl silicate ester support and process for production thereof

• US 5,686,372 A
• Filed: 05/26/1995
• Issued: 11/11/1997
• Est. Priority Date: 05/26/1995
• Status: Expired due to Fees

• Current Assignee: University Technologies, Inc. (University of Calgary)
• Original Assignee: University Technologies International, Inc.
• Inventors: Langford, Cooper H., Persaud, Lalchan, Lepore, Giuseppe P.
• Primary Examiner(s): Caldarola, Glenn A.
• Assistant Examiner(s): Preisch, Nadine
• Application Number:
  US08/451,650
• Time in Patent Office: 900 Days
• Field of Search: 502/254, 502/242
• US Class Current: 502/242
• CPC Class Codes: B01J 21/08 Silica
• CPC Class Codes: B01J 31/0212 Alkoxylates
• CPC Class Codes: B01J 31/0274 containing silicon ligands in coordination complexes B01J31/1608
• CPC Class Codes: B01J 35/30 characterised by their physical properties
• CPC Class Codes: B01J 35/39 Photocatalytic properties
• CPC Class Codes: B01J 37/0209 involving a reaction between the support and a fluid
• CPC Class Codes: Y02W 10/37 using solar energy

Abstract

A photocatalyst compound comprising a silica-based support material having bound thereto a photocatalyst selected from the group consisting of TiO₂, WO₃ and mixtures thereof, the photocatalyst compound having been derivatized by reaction with an alcohol compound. The process for producing the photocatalyst compound comprises the steps of: (i) contacting a silica-based support material having bound thereto a photocatalyst selected from the group consisting of TiO₂, WO₃ and mixtures thereof with an alcohol compound to form a slurry; (ii) maintaining the temperature of the slurry above the boiling point of the slurry to produce a substance having a modified surface consisting essentially of an alkyl silicate ester and esterified photocatalyst; and (iii) subjecting the substance to selective oxidation to oxidize the esterfied photocatalyst thereby producing a photocatalyst compound having a modified surface consisting essentially of an alkyl silicate ester and a photocatalyst substantially free of ester groups. The photocatalyst compound is useful, inter alia, in the treatment of a fluid containing an organic pollutant.

Claims

1. A photocatalyst compound comprising:

(i) a silica-based support material having a modified surface consisting essentially of an alkyl silicate ester; and

(ii) a photocatalyst selected from the group consisting of TiO₂, WO₃ and mixtures thereof bound to the silica-based support material, the photocatalyst being substantially free of ester groups.

2. The photocatalyst compound defined in claim 1, wherein the photocatalyst is TiO₂.

3. The photocatalyst compound defined in claim 1, wherein the silica-based support material is porous.

4. The photocatalyst compound defined in claim 1, wherein the silica-based support material is a silica gel.

5. The photocatalyst compound defined in claim 1, wherein the silica-based support material is a silica bead.

6. The photocatalyst compound defined in claim 1, wherein the TiO₂ is present in an amount of from about 0.05% to about 10% by weight of the photocatalyst compound.

7. The photocatalyst compound defined in claim 1, wherein the TiO₂ is present in an amount of from about 2% to about 8% by weight of the photocatalyst compound.

8. The photocatalyst compound defined in claim 1, wherein the TiO₂ is present in an amount of from about 2% to about 6% by weight of the photocatalyst compound.

9. A process for producing a photocatalyst compound comprising the steps of:

(i) contacting a silica-based support material having bound thereto a photocatalyst selected from the group consisting of TiO₂, WO₃ and mixtures thereof with an alcohol to form a slurry;

(ii) maintaining the temperature of the slurry above the boiling point of the slurry to produce a substance having a modified surface consisting essentially of;

an alkyl silicate ester and esterified photocatalyst; and

(iii) subjecting the substance to selective oxidation to oxidize the esterified photocatalyst, the alkyl silicate ester being substantially unaffected, thereby producing a photocatalyst compound having a modified surface consisting essentially of an alkyl silicate ester and a photocatalyst substantially free of ester groups.

10. The process defined in claim 9, wherein the photocatalyst is TiO₂.

11. The process defined in claim 9, wherein a portion of the TiO₂ is in a non-crystalline form.

12. The process defined in claim 9, wherein the alcohol has the formula

13. The process defined in claim 12, wherein R is a C₁ -C₁₅ alkyl group.

14. The process defined in claim 12, wherein R is n-octyl.

15. The process defined in claim 12, wherein R is n-butyl.

16. The process defined in claim 9, wherein silica-based support material is obtained by a process comprising the steps of:

(i) hydrolysing a non-ionic titanium compound to produce a colloidal suspension having an average particle size of less than about 250 Å

;

(ii) contacting a porous silica-based support material with the colloidal suspension to produce an impregnated support; and

(iii) calcining the impregnated support to produce the silica-based support material.

17. The process defined in claim 16, wherein the non-ionic titanium compound is selected from the group consisting of TiCl₄, Ti(OR)₄ and mixtures thereof, wherein R is a C₁ -C₁₀ alkyl group.

18. The process defined in claim 9, wherein silica-based support material is obtained by a process comprising the steps of:

(i) contacting a porous silica-based support material with a non-ionic titanium compound to produce a slurry;

(ii) hydrolysing the slurry to produce an impregnated support; and

(iii) calcining the impregnated support to produce the silica-based support material.

19. The process defined in claim 18, wherein the non-ionic titanium compound is selected from the group consisting of TiCl₄, Ti(OR)₄ and mixtures thereof, wherein R is a C₁ -C₁₀ alkyl group.

20. The process defined in claim 9, wherein silica-based support material is obtained by a process comprising the steps of:

(i) contacting a porous silica-based support material with a slurry of TiO₂ to produce an impregnated support; and

(ii) heating the impregnated support to a temperature of at least about 150°

C. to produce the silica-based support material.

21. The process defined in claim 9, wherein Step (iii) comprising subjecting the substance to photolysis in the presence of an oxidizing agent.

22. The process defined in claim 21, wherein photolysis is conducted using radiation having a wavelength less than about 380 nm.

23. The process defined in claim 21, wherein the oxidizing agent is selected from the group consisting of oxygen and air.