A diesel oxidation catalyst comprising a honeycomb substrate washcoated
with a mixture of clay, a refractory oxide and a zeolite is disclosed.
The washcoated substrate is subsequently deposited with a precious metal
catalyst and a sulfur oxidation suppressant. In a preferred embodiment,
the clay is acid-leached bentonite, the refractory oxide is zirconia or
titania, the zeolite is beta-zeolite or Y-zeolite or ZSM-5 or mordenite,
the precious metal catalyst is preferably platinum, and the sulfur
oxidation suppressant is vanadium or vanadium oxide or a combination
thereof