Method and apparatus for combination catalyst for reduction of NOx in combustion products
AssigneesExonMobil Research and Engineering Company, Caterpillar Inc.
InventorsRichard F. Socha, James C. Vartuli, El-Mekki El-Malki, Mohan Kalyanaraman, Paul W. Park
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Abstract
A method and apparatus for catalytically processing a gas stream passing therethrough to reduce the presence of NOx therein, wherein the apparatus includes a first catalyst composed of a silver containing alumina that is adapted for catalytically processing the gas stream at a first temperature range, and a second catalyst composed of a copper containing zeolite located downstream from the first catalyst, wherein the second catalyst is adapted for catalytically processing the gas stream at a lower second temperature range relative to the first temperature range.
Claims15
An apparatus for catalytically processing a gas stream passing therethrough to reduce the presence of NOx therein, said apparatus comprising:
- a first catalyst positioned in a relatively upstream portion of said gas stream, said first catalyst, comprising silver containing γ-alumina for catalytically processing the gas stream, said first catalyst having a first temperature at which peak NOx reducing catalytic activity occurs, said first catalyst being adapted for both converting a portion of the NOx directly to N2, another portion to nitrogen-containing intermediates, with a portion of NOx remaining;
- and
- a second catalyst positioned in a relatively downstream portion of said gas stream from said first catalyst, said second catalyst comprising copper containing ZSM-5 having a crystal size in the range of from about 0.5 μm to 2.0 μm and a silicon to aluminum ratio of about 50, and a copper content of about 3% by weight based on the total weight of the second catalyst, for catalytically processing the gas stream downstream from the first catalyst, said second catalyst having a second temperature at which peak NOx reducing catalytic activity occurs, said second catalyst being adapted to facilitate the reaction of the remaining NOx and intermediates for further reduction into N2, wherein the value of the second temperature is lower than the value of the first temperature.
A method for catalytically processing a gas stream to reduce the presence of NOx therein, said method comprising the steps of:
- positioning a first catalyst in a relatively upstream portion of said gas stream;
- positioning a second catalyst in a relatively downstream portion of said gas stream from said first catalyst;
- delivering the gas stream to said first catalyst comprising silver containing y-alumina for catalytically processing the gas stream, said first catalyst being adapted for both converting a portion of the NOx directly to N2, another portion to nitrogen-containing intermediates, with a portion of NOx remaining, wherein said first catalyst includes a first temperature at which peak NOx reducing catalytic activity occurs;
- and
- conveying the gas stream from the first catalyst to said second catalyst comprising copper containing ZSM-5 having a crystal size in the range of from about 0.5 μm to 2.0 μm and a silicon to aluminum ratio of about 50, and a copper content of about 3% by weight based on the total weight of the second catalyst, for catalytically processing the gas stream, wherein said second catalyst includes a second temperature at which peak NOx reducing catalytic activity occurs, said second catalyst being adapted to facilitate the reaction of the remaining NOx and intermediates for further reduction into N2, whereby the value of the second temperature is lower than the value of the first temperature.
Dependencies are inferred from the claim text.