Optimization of nanostructured materials for hydrocarbon abatement during the cold-start period of gasoline vehicles

Abstract

Air pollution poses a major environmental concern worldwide. In metropolitan areas, motor vehicle exhaust contributes a major source of contaminants. More restrictive legislations regarding automotive emissions resulting in a remarkable decrease in the amount of pollutants associated to new vehicles. With current three-way catalysts (TWC), a recognized challenge in preventing these emissions is the lack of treatment capacity of hydrocarbons (HC) and CO under cold-start conditions. Fresh catalysts start to operate at ca.170 ºC, but aged catalysts light-off at ca. 200-225 ºC. These catalysts need between 60 to 120 seconds to reach these temperatures and during this time, about 50 to 80% of unburned HCs and around 80% CO are emitted. To curb the HC emissions, the incorporation of an inorganic nanoporous material to act as a HC trap prior to the TWC, is one of the most promising solutions. Zeolites are often considered as HC trap materials due to their stability under a variety of conditions. Different zeolites and zeotypes, with varying pore dimensionality and pore network connectivity, have been studied as adsorbents for HC emission control during the cold-start period. However, none of the reported materials have demonstrated the necessary characteristics of a HC trap under very demanding operational conditions. In this sense, a priority goal is to find an adsorbent that fulfills this requirement.