DEVELOPMENT OF DIESEL OXIDATION CATALYSTS FOR HEAVY DUTY ENGINES

Flow-through diesel oxidation catalysts (DOC's) have been shown to be an effective means of reducing emissions from diesel engines. In this work, the further development of diesel oxidation catalysts for the control of emissions from heavy duty engines is illustrated. Laboratory reactor and engine dynamometer data obtained from engine-based accelerated poisoning and aging studies demonstrate that HC, CO and SO₂ oxidation by DOC's can be modified by adjusting platinum and vanadium loadings in alumina-based Pt/V catalyst formulations. The performance and durability of this type of catalyst system are demonstrated with several aging cycles on heavy-duty engines. The fresh performance of two catalyst systems was determined on both US Heavy Duty Transient and ECE-R49 Test cycles with a 1991 calibration Perkins Phaser 6.0 L engine. Gas phase emissions were reduced by a similar amount for both catalysts over both cycles (HC: 60-70%, CO: 45-75%). Particulate reduction was observed to be higher on the cooler US cycle (33-37%) relative to the hotter ECE Test cycle (6-21%). The formulation with lower SO₂ oxidation activity performed better for particulate (21% reduction) on the ECE cycle than one with higher SO₂ oxidation activity (6%). The aged performance (1156 hours over two cycles) of one formulation was determined on the US Heavy Transient Test cycle where aged particulate conversions of 38% were observed.