Solid-state 27 Al Nuclear Magnetic Resonance Investigation of Plasma-facilitated NO x Reduction Catalysts
- PDF / 132,340 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 34 Downloads / 178 Views
Craig F. Habeger Caterpillar Inc., Technical Center E/854, PO Box 1875, Peoria, Illinois 61656 (Received 19 February 2002; accepted 30 April 2002)
Aluminum coordination distribution for alumina catalysts supported on mesoporous silica was examined. It was shown that aluminum coordination correlates to activity of the catalysts for plasma-enhanced, selective catalytic reduction of NOx with propene. Catalysts were prepared by incorporating aluminum onto the surface of a mesoporous silica support via three different post-synthesis routes to produce varying aluminum coordination. Aluminum trichloride, sodium aluminate, and aluminum isopropoxide precursors were examined. High-resolution, solid state 27Al nuclear magnetic resonance was used to determine aluminum coordination distributions for the resulting catalysts. Unsaturated aluminum sites (i.e., structural defects) correlated with increased activity at high temperatures while tetrahedrally-coordinated aluminum or BrØnsted acid sites correlated with activity at low temperatures. I. INTRODUCTION
Considerable effort has been devoted toward developing methods for the efficient removal of NOx from diesel engine exhaust due to ever-pressing emission limitations imposed by the United States Environmental Protection Agency. Numerous studies have shown that catalytic reduction of NOx by hydrocarbons is a promising method for the removal of dilute NOx from exhaust containing a significant amount of oxygen.1–8 Many catalyst formulations have been proposed and tested, including zeolites, noble metals, and metal oxides such as alumina, zirconia, titania, and alumina-silica. For lower exhaust temperatures (
Data Loading...
