Process and catalyst for photocatalytic conversion of contaminants

• US 6,221,259 B1
• Filed: 03/08/1999
• Issued: 04/24/2001
• Est. Priority Date: 03/08/1999
• Status: Expired due to Term

• Current Assignee: KSE Limited
• Original Assignee: KSE Limited
• Inventors: Kittrell, James R.
• Primary Examiner(s): Hruskoci, Peter A.
• Application Number:
  US09/262,895
• Time in Patent Office: 778 Days
• Field of Search: 210/748, 210/759, 210/760, 210/762, 210/763, 210/908, 210/909, 423/247, 423/245.1, 423/245.3
• US Class Current: 210/748.14
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/1023 Palladium
• CPC Class Codes: B01D 2255/104 Silver
• CPC Class Codes: B01D 2255/106 Gold
• CPC Class Codes: B01D 2255/20707 Titanium
• CPC Class Codes: B01D 2255/20715 Zirconium
• CPC Class Codes: B01D 2255/30 Silica
• CPC Class Codes: B01D 2255/802 Photocatalytic
• CPC Class Codes: B01D 2257/206 Organic halogen compounds
• CPC Class Codes: B01D 2257/702 Hydrocarbons
• CPC Class Codes: B01D 2257/708 Volatile organic compounds V.O.C.'s
• CPC Class Codes: B01D 2257/93 Toxic compounds not provided for in groups B01D2257/00 - B01D2257/708
• CPC Class Codes: B01D 53/8662 Organic halogen compounds
• CPC Class Codes: B01D 53/8668 Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
• CPC Class Codes: B01D 53/8671 Removing components of defined structure not provided for in B01D53/8603 - B01D53/8668
• CPC Class Codes: C02F 1/32 with ultraviolet light
• CPC Class Codes: C02F 1/725 by catalytic oxidation
• CPC Class Codes: C02F 2101/322 Volatile compounds, e.g. benzene
• CPC Class Codes: C02F 2101/36 containing halogen
• CPC Class Codes: C02F 2305/10 Photocatalysts
• CPC Class Codes: Y10S 210/908 : Organic
• CPC Class Codes: Y10S 210/909 : Aromatic compound, e.g. pcb, phenol

Abstract

A process and catalyst for the conversion of contaminants in an oxygen containing contaminated stream comprises passing the oxygen containing contaminated stream over a photocatalyst comprising titanium, zirconium and silica while irradiating the foregoing catalyst with ultraviolet light.

Claims

1. A process for the photocatalytic oxidative destruction of contaminants from an oxygen containing fluid stream which comprises:

providing a photocatalyst comprising titanium in an amount of between about 0.001 wt % to about 2.0 wt %, zirconium in an amount of between about 0.001 wt % to about 2.0 wt %, and silica; and

passing said oxygen containing fluid stream over said photocatalyst while irradiating the photocatalyst with ultraviolet light of wave length less than or equal to about 400 nanometers to destroy said contaminants, wherein the amount of oxygen in the oxygen containing fluid stream is sufficient to substantially oxidize said contaminants.

2. A process according to claim 1 wherein said silica comprises silica gel and said titanium and zirconium are supported by said silica gel.

3. A process according to claim 1 or 2 wherein said catalyst further comprises a metal selected from the group consisting of platinum, palladium and mixtures thereof in an amount of between about 0.01 wt % to about 2.0 wt %.

4. A process according to claim 1 or 2 wherein said catalyst further comprises a metal selected from the group consisting of silver, gold and mixtures thereof in an amount of between about 0.01 wt % to about 2.0 wt %.

5. A process according to claim 1 or 2 wherein said catalyst further comprises a metal selected from the group consisting of platinum, palladium and mixtures thereof in an amount of between about 0.01 wt % to about 2.0 wt %, and a metal selected from the group consisting of silver, gold and mixtures thereof in an amount of between about 0.01 wt % to about 2.0 wt %.

6. A process according to claim 1 or 2 including passing said oxygen containing fluid stream over said photocatalyst such that the contact time of the fluid stream with said photocatalyst is between about 0.01 seconds to 10 minutes, wherein the contact time is defined as the ratio of the volume of the photocatalyst to the total volumetric flow rate of said fluid stream.

7. A process according to claim 6 wherein said fluid is gas.

8. A process according to claim 7 including passing said oxygen containing gas stream over said photocatalyst such that the contact time of the gas stream with said photocatalyst is between about 0.05 seconds to 1 minute, where the contact time is defined as the ratio of the volume of the photocatalyst to the total volumetric flow rate of said gas stream.

9. A process according to claim 7 including passing said oxygen containing gas stream over said photocatalyst such that the contact time of the gas stream with said photocatalyst is between about 0.1 seconds to 5.0 minute, where the contact time is defined as the ratio of the volume of the photocatalyst to the total volumetric flow rate of said gas stream.

10. A process according to claim 6 wherein said fluid stream is an aqueous stream.

11. A process according to claim 10 including passing said oxygen containing aqueous stream over said photocatalyst such that the contact time of the aqueous stream with said photocatalyst is between about 0.5 seconds to 5 minutes, where the contact time is defined as the ratio of the volume of the photocatalyst to the total volumetric flow rate of said aqueous stream.

12. A process according to claim 1 wherein the amount of oxygen in the oxygen containing fluid stream is present in an amount, with respect to said contaminants, of at least 2 times stoichiometric.

13. A process according to claim 1 or 2 wherein said contaminants are selected from the group consisting of volatile organic compounds (VOCs), chlorinated volatile organic compounds (CVOs), toxic air pollutants (TAPs), and mixtures thereof.

14. A process according to claim 1 or 2 wherein said contaminants are organic contaminants and include compounds of carbon and hydrogen.

15. A process according to claim 1 or 2 wherein the process is carried out under the following conditions:

a temperature of between about 50°

F. to about 200°

F.;

pressure of between about 0.1 to about 10 atm.

16. A process according to claim 1 or 2 wherein the process is carried out under the following conditions:

a temperature of between about 70°

F. to about 150°

F.;

pressure of between about 0.8 to about 1.5 atm.

17. A process according to claim 1 or 2 wherein the process is carried out under the following conditions:

a temperature of ≦

1000°

F.

18. A process according to claim 1 or 2 wherein the ultraviolet light has a wave length of between about 185 to about 375 nanometers.

19. A process according to claim 1 or 2 wherein the photocatalyst has relative UV light transmission of at least about 200 microwatts/cm².

20. A process according to claim 1 or 2 wherein the ultraviolet light has an incident intensity on the exterior surface of the photocatalyst of at least about 0.1 mw/cm².

21. A process according to claim 1 or 2 wherein the ultraviolet light has an incident intensity on the exterior surface of the photocatalyst of between about 5 mw/cm² to 500 mw/cm².

22. A process according to claim 1 or 2 wherein the photocatalyst has the follow physical properties:

pore volume≧

0.4 cm³/g;

surface area≧

100 m²/g; and

a water saturation capacity of ≦

7 wt. % at 10% relative humidity air at 70°

F.

23. A process according to claim 2 wherein the photocatalyst has the follow physical properties:

pore volume preferred 0.4 to 1.5 cm³/g;

surface area preferred 100 to 400 m²/g; and

a water saturation capacity of ≦

5 preferred at 10% relative humidity air at 70°

F.

24. A process according to claim 1 wherein the photocatalyst comprises titanium in an amount of between about 0.005 wt % to about 0.500 wt. % and zirconium in an amount of between about 0.005 wt. % to about 0.500 wt. %.

25. A process according to claim 1 wherein the photocatalyst comprises titanium in an amount of between about 0.008 wt % to about 0.080 wt. % and zirconium in an amount of between about 0.008 wt. % to about 0.080 wt. %.