REMOVAL OF NITROGEN OXIDES FROM GASES

摘要

For selectively removing nitrogen oxides from a carrier gas that contains hydrocarbons, the nitrogen oxides are removed by chemisorption on metal oxides, without the occurrence of undesirable secondary reactions. The metal oxides are preferably formed from metals of the 6th to 8th subgroups, whereby manganese dioxide (MnO2) is especially preferred as a metal oxide. The process can be cond ucted with one or more reactor beds, which preferably operate at 10 to 40.degree.C and are regenerated with nitrogen at a temperature of 130 to 170.degree.C. By removing nitrogen oxides from an olefin-rich gas, for example from the waste gas of an FCC unit, the resultant gas can then be fed to a cryogenic olefi n extraction stage without danger of explosion. Such a waste gas contains unsaturated hydrocarbons, hydrogen, carbon monoxide, and oxygen, the oxygen having a concentration preferably between 100 a nd 5000 mol ppm.