Abstract
This paper reports the results of an experimental study on adsorption of light hydrocarbons on small pore microporous materials. The choice of hydrocarbons studied was affected taking into consideration the application of adsorption processes in removal of light hydrocarbons from exhaust streams of the petrochemical industry and of light-duty gasoline vehicles under cold start conditions (C4-C5 paraffins and olefins). The materials investigated were 5A and Ferrierite zeolites, characterized by different pore opening and Si/Al ratio. Equilibrium isotherm curves at room temperature were determined by a gravimetric method on dehydrated zeolites, while breakthrough curves in dynamic tests were used to evaluate the adsorption properties of hydrated zeolites at low hydrocarbon partial pressure (0-1 kPa) and in experimental conditions close to those of a HC trap at the engine exhaust. The experimental results regarding the adsorption capacities were discussed with the aim to understand how the physico-chemical characteristics of the adsorbent material could affect its trapping capability in adsorbing different types of hydrocarbons.
Highlights
The adsorption processes are widely employed for light hydrocarbons (HC) capture in applications that require the recovery of these compounds in high purity [1,2] and have been recently proposed for the abatement of organic pollutants at the exhaust of light-duty gasoline vehicles under cold start conditions [3].This last application is justified by the future legislative limits for passenger car emissions in EU and USA that will become more and more stringent and will require the development of new technological solutions, including more effective after-treatment devices
The choice of hydrocarbons studied was affected taking into consideration the application of adsorption processes in removal of light hydrocarbons from exhaust streams of the petrochemical industry and of light-duty gasoline vehicles under cold start conditions (C4 - C5 paraffins and olefins)
Adsorption properties of 5A and Ferrierite zeolites towards light paraffins and olefins have been investigated at 298 K by equilibrium isotherms obtained by gravimetric and by dynamic tests in flow microreactor
Summary
The adsorption processes are widely employed for light hydrocarbons (HC) capture in applications that require the recovery of these compounds in high purity (petrochemical industry) [1,2] and have been recently proposed for the abatement of organic pollutants at the exhaust of light-duty gasoline vehicles under cold start conditions [3]. It is known that the largest fraction (more than 80%) of the total organic pollutants flows out during the short time following the engine startup (200 seconds) During this period the air/fuel ratio is on the rich side, which implies more HC emissions, while the temperature of the threeway catalyst (TWC) is lower than its light-off value (473 - 573 K), which requires between 60 to 120 s to be reached. The evaluation of adsorption properties was affected by equilibrium isotherms and dynamic tests in flow micro-reactor at room temperature
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