Diesel oxidation catalyst layer structure for enhanced hydrocarbon conversion

Composite laminate diesel oxidation catalyst for treating exhaust gas emissions from a diesel engine comprising: (a) a carrier substrate; (B) a lower layer coated on said carrier substrate comprising at least a first zeolite; (C) a middle layer coated on said lower layer comprising at least one precious metal component on a refractory metal oxide support and which is substantially free of a molecular sieve; and (d) a top layer coated on said middle layer comprising at least one second zeolite, wherein the lower layer further comprises activated gamma alumina and platinum component; wherein the refractory metal oxide of the middle layer comprising gamma alumina activated, wherein the at least one precious metal component of the middle layer comprises a platinum component and palladium component, and wherein the top layer further it comprising activated gamma alumina and platinum component.