Tailoring the polarity of 13X zeolite with glycine for efficient capture of oxygenates from Fischer-Tropsch oil

Abstract

Although 13X zeolite is commonly used to remove oxygenates from Fischer-Tropsch oil, it still suffers from limited adsorption selectivity. In this study, glycine was used as a modifier to functionalize 13X zeolite by grafting polar groups, and applied for the removal of oxygenates from Fischer-Tropsch oil. The results indicate that the modified zeolite exhibits a high adsorption capacity for oxygenates. Specifically, the adsorption capacity for butanol, hexanal, and 2-hexanone increased by approximately 90 %, reaching 0.60 g·g⁻¹, 0.36 g·g⁻¹, and 0.35 g·g⁻¹. The adsorption capacity for hexanol and octanol increased by approximately 50 %. The enhancement in adsorption capacity for carbonyl compounds and long-chain alcohols (such as hexanol, heptanol, and octanol) was particularly notable, with an average increase of about 80 %. Mechanistic studies revealed that the adsorption of oxygenates on the modified zeolite is primarily physical adsorption, involving hydrogen bonding interactions and van der Waals forces. The adsorption process can be divided into two stages: surface adsorption and pore diffusion, and is jointly influenced by factors such as zeolite pore size, adsorbate molecular size, and their interactions with the pore channels. This study provides a novel strategy for the removal of oxygenated compounds from Fischer-Tropsch oil.