Influence of homogeneous decane oxidation on the catalytic performance of lean NO x catalysts

Extensive homogeneous gasphase reactions were observed when decane was used as the hydrocarbon reductant for the selective reduction of NO _x . The catalytic performance of a SnO₂/CoO _x /Al₂O₃ catalyst was found to be strongly dependent on the extent of the homogeneous reaction in the precatalytic volume. The effect of the homogeneous reaction on the catalytic performance also depended on whether SO₂ was present in the feed. By filling the precatalytic volume with 25–35 mesh irregularly shaped quartz chips, gasphase reaction was suppressed significantly. This methodology was used to evaluate the inherent catalytic performance of SnO₂/CoO _x /Al₂O₃ and SnO₂/Al₂O₃ catalysts with decane as a reductant. It was found that in the absence of SO₂, SnO₂/Al₂O₃ was a better catalyst than SnO₂/CoO _x /Al₂O₃, but in the presence of 30 ppm of SO₂ the latter was a far better catalyst.