US 7,090,811 B2 · Method of reducing NOx in diesel engine exhaust

Abstract

This invention provides a method of reducing nitrogen oxides in an oxygen containing exhaust stream using ethanol as a reductant for plasma-assisted selective catalytic reduction. The exhaust gas, generated from a diesel engine or other lean-burn power source, comprises nitrogen oxides, especially NO. Ozone generated from a plasma reactor is injected into the exhaust stream to convert NO to NO2 and the plasma injection is followed by the addition of ethanol. The NO2 is then reduced by contacting the exhaust stream with a dual-bed catalytic reactor comprising BaY (or NaY) and CuY zeolite catalysts in the presence of ethanol as the reductant. The plasma power density and the molar ratio of ethanol to NOx fed to the catalytic reactor are controlled as a function of the catalyst temperature for the best performance of the plasma-catalyst system. An average conversion of NOx to N2 of at least 90% is achieved over the temperature range of 200–400° C.

Claims14

Dependent claims

A method of reducing nitrogen oxides, including NO, in an exhaust stream also comprising oxygen, carbon monoxide and hydrocarbons at a temperature above about 150° C., said method comprising:

passing air through a non-thermal plasma reactor to generate an ozone containing plasma and adding said plasma to said exhaust stream for oxidation of NO to NO2;
adding ethanol to said exhaust stream, separately from the addition of said plasma, for the reduction of said nitrogen oxides;
and
thereafter contacting said exhaust stream with a dual bed reduction catalyst comprising NaY zeolite and/or BaY zeolite in the first bed and CuY zeolite in the second bed to reduce said nitrogen oxides to N2.

1 more element

A method of reducing nitrogen oxides, NOx including NO, in a diesel engine exhaust stream also comprising oxygen, carbon monoxide and hydrocarbons at a temperature above about 150° C., said method comprising:

(a) passing said exhaust stream into contact with an oxidation catalyst to oxidize said carbon monoxide and hydrocarbons;
(b) passing air through a non-thermal plasma reactor to generate an ozone containing plasma and adding said plasma into said exhaust stream for oxidation of NO to NO2, the energy applied to said plasma reactor being inversely proportional to the temperature of the reduction catalyst at temperatures in the range of about 150° C. to 400° C. with said energy being reduced to zero at temperatures of about 350° C. and higher;
(c) adding ethanol to said exhaust stream for the reduction of said nitrogen oxides, the amount of said ethanol being increased in proportion to the reduction catalyst temperature;
and thereafter
(d) flowing said exhaust stream through a dual-bed catalytic reduction reactor, said reactor comprising a first bed consisting essentially of barium and/or sodium Y zeolite catalyst and a second bed consisting essentially of copper Y zeolite catalyst, where the volume of said first bed is larger than the volume of said second bed.

2 more elements

Dependencies are inferred from the claim text.

Method of reducing NOx in diesel engine exhaust

Life of this patent

Method of reducing NOx in diesel engine exhaust

Life of this patent

Abstract

Claims14