Abatement of hydrocarbons by acid ZSM-5 and BETA zeolites under cold-start conditions

Simulated cold-start tests have been carried out to evaluate the performance of H-ZSM-5 and H-BETA zeolites as hydrocarbon traps under simulated gasoline car exhaust gases, paying special attention to the effect of water on their behaviour. It is concluded that the hydrothermal treatment of the zeolites in the acidic form contributes to the better performance of these materials as hydrocarbon traps since the stabilization of the zeolites takes place. Moreover, the decrease of the surface acidity of the zeolites results in an increase of the Si/Al ratio, which contributes to the decrease of the water affinity for adsorption sites. Thus, the competition with hydrocarbon molecules in the exhaust for the adsorption sites is reduced which increases their trap efficiency. The stabilized H-ZSM-5 is the zeolite that showed the best performance with a propene offset temperature of 240 °C, which should be high enough for the three-way catalyst to carry out its role as catalytic converter.

The authors would like to thank Spanish Ministerios de Ciencia e Innovación – CSIC (Project 201080I031) y de Medio Ambiente y Medio Rural y Marino (Project 331/PC08/3-13.1) and Generalitat Valenciana and FEDER (PROMETEO/2009/047) for financial support. B. Puértolas thanks the Ministry of Education of Spain for FPU Grant (FPU Grant AP2009-3544), Dr. López contract is financed by Ramon y Cajal contract (RYC-2009-04483) and F.J. Varela-Gandía thanks the University of Alicante for the PhD studentship.