Ambient Temperature Hydrocarbon Selective Catalytic Reduction of NO_<i>x</i> Using Atmospheric Pressure Nonthermal Plasma Activation of a Ag/Al₂O₃ Catalyst

Atmospheric pressure nonthermal-plasma-activated catalysis for the removal of NO_<i>x</i> using hydrocarbon selective catalytic reduction has been studied utilizing toluene and <i>n</i>-octane as the hydrocarbon reductant. When the plasma was combined with a Ag/Al₂O₃ catalyst, a strong enhancement in activity was observed when compared with conventional thermal activation with high conversions of both NO_<i>x</i> and hydrocarbons obtained at temperature ≤250 °C, where the silver catalyst is normally inactive. Importantly, even in the absence of an external heat source, significant activity was obtained. This low temperature activity provides the basis for applying nonthermal plasmas to activate emission control catalysts during cold start conditions, which remains an important issue for mobile and stationary applications

Redispersion of Gold Supported on Oxides

Although many gold heterogeneous catalysts have been shown to exhibit significant activity and high selectivity for a wide range of reactions in both the liquid and gas phases, they are prone to irreversible deactivation. This is often associated with sintering or loss of the interaction of the gold with the support. Herein, we report on the use of methyl iodide as a method of dispersing gold nanoparticles supported on silica, titania, and alumina supports. In the case of titania- and alumina-based catalysts, the gold was transformed from nanometer particles into small clusters and some atomically dispersed gold. In contrast, although there was a drop in the gold particle size on the silica support following CH₃I treatment, the size remained in the submicrometer range. The structural changes were correlated with changes in the selectivity and activity for ethanol dehydration and benzyl alcohol oxidation. From these observations, it is clear that this treatment provides a method by which deactivated gold catalysts can be reactivated via redispersion of the gold