| 摘要 |
<p>A catalyst assembly effective for selective catalytic reduction of nitrogen oxides with ammonia in a gas stream has an upstream section comprising a phosphorus getter comprised of a phosphorus retaining material, e.g., activated alumina, and a downstream section comprising a vanadium oxide containing catalyst, e.g., a vanadia/titania catalyst. It has surprisingly been found that vanadium oxide catalysts are poisoned by phosphorus which may be contained in the form of phosphorus contaminant compounds in the gas to be treated, so that the positioning of a phosphorus-retaining material upstream of the catalyst prolongs catalyst life. In operation, the gas to be treated is passed first through the phosphorus getter upstream section of the catalyst assembly and then contacted in the presence of ammonia with the downstream section catalytic material.</p> |
