Process for decoating a washcoat catalyst substrate
The invention relates to a process for decoating a used washcoat carrier substrate to produce a clean, inert carrier or substrate. In a preferred embodiment, a process according to the invention includes treating a washcoat catalyst substrate in an aqueous solution including a dispersant, an emulsifier, and at least one of an acid and a base. Alternatively, the first solution may include sodium hydroxide, sodium bicarbonate, or aluminum bicarbonate. The substrate is also subject to ultrasonic treatment, while treating the substrate in an aqueous solution preferably including a dispersant. The substrate may ultimately be rinsed, for example in deionized water. During treatment, solutions may be agitated, for example by air injection, directed stream of water or other agitation. Optional embodiments include heating prior to immersion, the addition of a solvent to solution; rinsing between steps, for example with DI water; treatment with acid to remove sodium before final rinsing, final rinsing in a cascade system, and drying.
1. A method of removing catalytic material from a catalyst substrate, comprising:
treating a substrate in a first aqueous solution maintained at a temperature of 10° to 90° C., the first aqueous solution comprising an emulsifier having a hydrophile-lipophile value of from 2 to 19, and at least one of an acid and a base; and
treating the substrate in a second aqueous solution maintained at a temperature of 10° to 90° C., while subjecting the substrate to an ultrasonic treatment.
2. The method according to claim 1 , wherein the first aqueous solution further includes a solvent.
3. The method according to claim 2 , wherein the solvent includes at least one of dipropylenemethyl ether and triethanol amine.
4. The method according to claim 1 , wherein the first aqueous solution includes NaOH.
5. The method according to claim 4 , wherein the first aqueous solution includes NaOH at a concentration of 3 to 5 percent by weight.
6. The method according to claim 1 , further comprising, following the treatment with the first aqueous solution:
applying agitation to the first aqueous solution so that a directed stream of the first aqueous solution is directed towards at least part of the substrate.
7. The method according to claim 1 , wherein the second aqueous solution includes a dispersant, an emulsifier, and at least one of an acid and a base.
8. The method according to claim 7 , wherein the first aqueous solution includes NaOH and the second aqueous solution includes NaOH.
9. The method according to claim 8 , further comprising, following ultrasonic treatment:
treating the substrate in an aqueous solution comprising acid at a concentration of 0.5 to 5.0 percent by weight.
10. The method according to claim 8 , further comprising, following ultrasonic treatment:
treating the substrate in an aqueous solution comprising a base at a concentration of 0.5 to 5.0 percent by weight.
11. The method according to claim 1 , further comprising rinsing the substrate in a cascade washing system having a plurality of chambers, wherein water flows through the plurality of chambers from a first chamber to a last chamber, and wherein the substrate is moved periodically through the plurality of chambers from the last chamber to the first chamber.
12. The method of claim 1 , wherein the emulsifier is a polyester-based emulsifier.
13. The method of claim 1 , wherein the emulsifier is an ethoxylated emulsifier.
14. A method of removing catalytic material from a catalyst substrate, comprising:
heating the substrate to between 300° and 400° F.;
treating a substrate in a first aqueous solution maintained at a temperature of 10° to 90° C., wherein the first aqueous solution includes an emulsifier, and at least one of an acid and a base;
rinsing the substrate; and
treating the substrate in a second aqueous solution maintained at a temperature of 10° to 90° C., while subjecting the substrate to an ultrasonic treatment wherein the second aqueous solution includes a dispersant and at least one of an acid and a base.
15. The method according to claim 14 , wherein the first aqueous solution includes NaOH at a concentration of 3 to 5 percent by weight.
16. The method according to claim 14 , wherein the second aqueous solution includes NaOH at a concentration of 3 to 5 percent by weight.
17. The method according to claim 12 , wherein the first aqueous solution includes NaOH at a concentration of 5 to 10 percent by weight and an organic solvent.
18. The method according to claim 17 , wherein the first aqueous solution further includes a solvent.
19. The method according to claim 17 , wherein the second aqueous solution includes NaOH at a concentration of 5 to 10 percent by weight and an organic solvent.
20. The method according to claim 12 , wherein the first aqueous solution includes sodium bicarbonate at a concentration of 3 to 10 percent by weight.
21. The method according to claim 20 , wherein the first aqueous solution includes ammonium bicarbonate at a concentration of 3 to 10 percent by weight.