Investigação da adsorção de compostos nitrogenados e sulfurados em amostras de diesel

Abstract

New technological routes have been studied to facilitate the hydrotreating process (HDT) that is used nowadays to reduce sulfur contents in fuels due to the increase of environmental restrictions related to sulfur content in diesel. The HDT requires a high consumption of energy and hydrogen. The presence of nitrogen compounds demands this process to be more difficult. Among the alternative technological routes, adsorption can be mentioned. In the present work, the adsorption of sulfur and nitrogen compounds present in two diesel samples on three commercial adsorbents, silica, clay and carbon, was evaluated. Kinetic profiles, adsorption isotherms and breakthrough tests were performed. For modeling kinetics and breakthrough data, mass transfer models were used. These results indicated that the adsorbents presented a higher affinity to nitrogen compounds than to sulfur compounds. The equilibrium isotherms for diesel A showed that silica and clay adsorbents removed a larger amount of sulfur and nitrogen compounds, respectively. The effective diffusivity values calculated using the kinetics profiles indicated a lower diffusion resistance for sulfur and nitrogen compounds in the presence of silica. For diesel B, the equilibrium isotherm data showed that, due to its high viscosity, the increase of temperature allows a better accessibility of the adsorbates to adsorption sites. Breakthrough tests for diesel B showed smoothed profiles that can be related to the presence of different families of compounds, which saturate the adsorbent after different times, or to diffusion problems.