Adsorptive Selectivity and Mechanism of Three Different Adsorbents for Nitrogenous Compounds Removal from Microalgae Bio-Oil

Microalgae bio-oil is of interest as a potential alternative to traditional fossil-fuel-based transportation fuels. However, the presence of nitrogenous compounds in the bio-oil can lead to the release of NOx (a polluting gas) during combustion, and is detrimental to the environment. Thus, it is necessary to selectively remove these compounds from the bio- Cu-Y zeolite oil prior to the bio-oil being used as a transportation fuel. This study investigates the adsorptive capacity, selectivity, and mechanism of three adsorbents, Cu-zeolite Y, silica gel, and activated carbon, for the removal of nitrogen-containing compounds from bio-oils derived from pyrolysis of the microalga Tetraselmis suecica. Since Cu cations preferentially adsorb nitrogen over oxygen, the affinity of Cu-zeolite Y for nitrogen could allow denitrogenation of microalgae bio-oils. Moreover, when Cu-zeolite Y was used for selective denitrogenation, the presence of the compounds containing aromatic rings such as benzocyclobutene and phenol would not substitute indole or hexadecanamide. The adsorptive selectivity of the silica gel depends on the acid-base interaction. Hydrogen bond interaction and acid-base interaction play an important role in adsorptive denitrogenation over the activated carbon. This study found that activated carbon is a promising adsorbent for the removal of nitrogenous compounds from microalgae bio-oil.