Direct NOx decomposition catalyst with improved activity and selectivity
A catalyst for direct decomposition of NO and NO 2 to N 2 and O 2 has a CoFe 2 O 4 spinel doped with potassium cations. The catalyst has high activity and good selectivity for N 2 production, when potassium cations are loaded at a density of about 0.9 weight percent. Methods for making the catalyst include wet impregnation of a CoFe 2 O 4 spinel with a solution of potassium cations, such as a KOH solution.
1. A catalytic converter for the direct decomposition removal of NO x from an exhaust gas stream flowing at a temperature of from about 400° C. to about 650° C., the catalytic converter comprising:
an inlet configured to receive the exhaust gas stream into an enclosure;
an outlet configured to allow the exhaust gas stream to exit the enclosure; and
a catalyst system contained inside the enclosure, the catalyst system comprising CoFe 2 O 4 spinel in a nanoparticle form, having an average diameter of from about 2 nm to about 100 nm; and
potassium cations doped in the spinel.
2. The catalytic converter as recited in claim 1 , wherein the potassium cations are present at a weight percentage within a range of from about 0.5 to about 2.0%.
3. The catalytic converter as recited in claim 1 , wherein the potassium cations are present at a weight percentage within a range of from about 0.5 to about 1.5%.
4. The catalytic converter as recited in claim 1 , wherein the potassium cations are present at a weight percentage within a range of from about 0.7 to about 1.2%.
5. The catalytic converter as recited in claim 1 , wherein the potassium cations are present at a weight percentage within a range of from about 0.85 to about 0.95%.
6. A method for direct decomposition removal of NO x from a gas mixture, the method comprising:
exposing a gas mixture having NO x to a catalyst including a CoFe 2 O 4 spinel doped with potassium cations at a loading density within a range of from about 0.5 to about 2.0 weight percent; and
catalyzing a direct decomposition of the NO x to generate N 2 without the presence of a reductant.
7. The method as recited in claim 6 , wherein the step of exposing the gas mixture to the catalyst can include passing the gas mixture having NO x over the catalyst at a temperature within a range of 450-650° C.
8. The method as recited in claim 7 , wherein the gas mixture is an exhaust stream from an internal combustion engine.
9. The method as recited in claim 6 , wherein the potassium cations are present at a weight percentage within a range of from about 0.5 to about 2.0%.
10. The method as recited in claim 6 , wherein
the potassium cations are present at a weight percentage within a range of from about 0.5 to about 1.5%.
11. The method as recited in claim 6 , wherein
the potassium cations are present at a weight percentage within a range of from about 0.7 to about 1.2%.
12. The method as recited in claim 6 , wherein the potassium cations are present at a weight percentage within a range of from about 0.85 to about 0.95%.