Hydrocarbon radicals and nitroxy complexes on the surface of HZSM-5 and CuZSM-5 zeolites: An ESR study

The conditions favorable for the formation of oligomer and benzene cation r adicals upon C2H4, C6H6, and C3H6 adsorption on thermally activated HZSM-5 and CuZSM-5 zeolites were studied. In the case of isolated copper ions, the radicals were shown to be formed from C3H6 but not from C2H4 and C6H6 Para magnetic nitroxy complexes, which were formed as a result of the interactio n of adsorbed hydrocarbons C2H4, C6H6 and C3H6 with NO and NO2, were reveal ed on HZSM-5 zeolite and Al2O3. Hydrocarbon radicals and nitroxy complexes are localized on different zeolite sites. Nitroxy complexes are formed on a luminum cations. The role of radicals and nitroxy complexes in the process of NOx selective catalytic reduction by hydrocarbons on the zeolites was di scussed on the basis of the temperature dependences of the concentrations o f these species.