Wang Yaming

Influence of ZrO 2 /Al 2 O 3 Ratio in Carrier on Performance of Pt/ZrO 2 -Al 2 O 3 Catalyst

Abstract Diesel engines have been more and more widely used in heavy duty vehicles because of high efficiency and low fuel consumption compared with petrol engines. Taking ZrO2 as the additive, the influence of the mass ratio of ZrO2 to Al2O3 on catalytic performance was studied. The results show that, with an increase of ZrO2 doping, the Pt particles become smaller at first and then larger in the catalyst. The interaction between Pt and the carrier increases, and then decreases. Analysis of the activity data shows the optimized doping amount of ZrO2 is 40 wt% the complete oxidation temperatures of CO and C3H6 are reduced by 20 and 25 oC, respectively. When the ZrO2/Al2O3 mass ratio in the carrier is varied, the precious metal dispersion on the catalyst and the precious metals interaction with the carrier are different with varying levels. The smaller the Pt particle size, the stronger the interaction between precious metal and the carrier, and the performance of catalyst is improved.

Preparation and Application of the HCA Catalyst Materials

Abstract To adsorb the excess hydrocarbons emitted during a period of engine cold-start and to solve the fault that Hydrocarbon (HC) adsorption behavior on Pd-based catalyst appears during a cold-start period of actual driving cycle in the vehicles of Dragon and Cherry, Hydrocarbon Absorber (HCA) material were leaded in catalytic performance of prepared HCA catalyst and HC adsorption process were tested, and then their applications were studied in the whole vehicle. In this work, Pd/Ce-HZSM-5 was used as the main recipes of HCA materials as well as a combination of zeolite and precious metals. Since Pd-based catalyst shows relatively good light-off performance, the combination of HC adsorption and early light-off activity has led to an improvement of overall HC emission reduction to Pd/Ce-HZSM-5. Usage of zeolite combined with Pd-based catalyst maximizes HC adsorption between 20∼30 s during the cold-start period for fresh catalyst. For Dragon and Cherry models, their emission results show Pd/Ce-HZSM-5 catalyst is superior to Al2O3 molecular sieve catalyst for HC trap. HCA material has great research potential to meet high standards of HC emissions quality at low temperature.