Control of hydrocarbon cold-start emissions: A search for potential adsorbents

A principle of single-file diffusion has been successfully employed to control automotive hydrocarbon (HC) emissions particularly during the cold-start period. Temperature programmed desorption technique of toluene and ethylene, as probe sorbates, was employed to screen a series of as synthesized one-dimensional molecular sieves as potential HC traps. Ethylene was found to be trapped to varying degrees by the larger toluene molecules within the 1-D pores of the synthesized samples. In particular, ZSM-12 and SAPO-5 showed superior trapping performance for both sorbates. ZSM- 12 was selected as a better candidate because of its higher temperature of desorption maximum for ethylene (150 degrees C), which is comparable to the light-off temperature of automotive catalytic converter. It was also found that this adsorbent was stable up to the desired temperature of operation i.e., 800 degrees C, however with some reduction in ethylene trapping capacity. (C) 2007 Elsevier Inc. All rights reserved.