Catalyst and process for oxidation and removal of nitrogen oxides (NOx) from combustion gases

摘要

A bi-functional oxidation catalyst and process for catalytic oxidation and removal of nitrogen oxides (NOx) from combustion gases derived from combustion of carbonaceous fuels such as coal, oil, or natural gas. The bi-functional catalyst includes adsorption and oxidation function metal oxides provided in adjacent close intimate contact by utilizing a binding agent, such as carboxylic acid and calcining to provide a metal oxide complex having a crystalline form. Such nitrogen oxides (NOx) contained in the combustion gases are initially catalytically oxidized to at least about 50 vol % NO2 and some higher oxides by contact with the bi-functional catalyst at 170-550° F. temperature. The combustion gas containing the partially oxidized NOx is then preferably further chemically oxidized by being mixed with a chemical oxidant such as ozone (O3) in a molar ratio of the chemical oxidant3 to NOx in the range of 0.5:1-1.2:1 to produce higher oxides of nitrogen such as substantially N2O5. The further treated combustion gas containing the N2O5 is next scrubbed with a suitable scrubbing liquid such as water to effectively remove the nitrogen oxides (NOx) and produce a clean treated flue gas stream containing less than about 15 ppm nitrogen oxides and suitable for environmentally safe discharge to the atmosphere.