METHOD FOR REMOVING A CATALYST INHIBITOR FROM A SUBSTRATE
This invention is directed to a process for removing a catalyst inhibitor from a substrate or catalytic converter containing at least one nitrogen oxide (NO x ) catalyst using a phosphoric acid composition. The process is particularly suited for removing the catalyst inhibitor, arsenic, from a fly ash-coated substrate or converter. A substantial amount of catalyst inhibitor can be removed from a fly ash-coated catalytic converter without removing a significant portion of one or more of the NO x reduction catalysts in or on the substrate.
1 . A method for removing a catalyst inhibitor from a catalytic converter having a substrate and at least one NO x reduction catalyst, comprising:
contacting the catalytic converter with a phosphoric acid composition to remove at least a portion of the catalyst inhibitor from the catalytic converter; and
rinsing the catalytic converter with an aqueous composition to remove at least a portion of the phosphoric acid composition.
2 . The method of claim 1 , wherein the catalyst inhibitor comprises arsenic.
3 . The method of claim 1 , wherein the catalytic converter that is contacted with the phosphoric acid composition is a fly ash-coated catalytic converter.
4 . The method of claim 1 , wherein the substrate is a metal, metal oxide, or ceramic substrate.
5 . The method of claim 1 , wherein the NO x reduction catalyst comprises at least one metal selected from the group consisting of Group 4, 5 and 6 metals.
6 . The method of claim 1 , wherein the phosphoric acid composition contacting the catalytic converter contains at least 1 wt % phosphoric acid, based on total weight of the composition contacting the filter.
7 . The method of claim 1 , wherein the phosphoric acid composition comprises at least one surfactant.
8 . The method of claim 1 , wherein the aqueous composition is comprised of at least 50 wt % water.
9 . The method of claim 1 , The method of claim 1 , wherein the catalytic converter is contacted with the phosphoric acid composition at an average pH of not greater than 4.
10 . The method of claim 1 , wherein the catalytic converter is contacted with the phosphoric acid composition at an average temperature of from 10° C. to 90° C.
11 . The method of claim 1 , wherein the catalytic converter is agitated while being contacted with the phosphoric acid composition.
12 . The method of claim 1 , wherein the rinsed catalytic converter is impregnated with at least one NO x removal catalyst.
13 . A method for removing a catalyst inhibitor from a metal, metal oxide, or ceramic substrate, comprising:
contacting the substrate with a phosphoric acid composition to remove at least a portion of the catalyst inhibitor from the substrate; and
rinsing the substrate with an aqueous composition to remove at least a portion of the phosphoric acid composition.
14 . The method of claim 13 , wherein the substrate includes at least one NO x reduction catalyst.
15 . The method of claim 14 , wherein the at least one NO x reduction catalyst is comprised of a metal selected from the group consisting of Group 4, 5 and 6 metals.
16 . The method of claim 13 , wherein the catalyst inhibitor comprises arsenic.
17 . The method of claim 13 , wherein the substrate that is contacted with the phosphoric acid composition is fly ash-coated.
18 . The method of claim 13 , wherein the phosphoric acid composition contacting the substrate contains at least 1 wt % phosphoric acid, based on total weight of the composition contacting the filter.
19 . The method of claim 13 , wherein the phosphoric acid composition comprises at least one surfactant.
20 . The method of claim 13 , wherein the substrate is contacted with the phosphoric acid composition at an average pH of not greater than 4.