Desorption kinetics of water on hydrophobic core–shell iron-based Fischer–Tropsch synthesis catalysts

Abstract

Inhibiting the occurrence of the water gas shift (WGS) reaction and developing catalysts with low CO₂ selectivity remain the focus of researchers in Fischer–Tropsch synthesis. To further investigate the impact of hydrophobic modification on the WGS reaction, we designed a hydrophobic core–shell Fe₂O₃@Si-CH₃ catalyst, which exhibited a low CO₂ selectivity of 1.65% at 31.57% CO conversion. Then, an improved temperature-programmed desorption (TPD) technology was employed to investigate the desorption kinetics of water molecules on both hydrophilic and hydrophobic catalysts. The kinetic parameters were ascertained by varying the heating rate. The results demonstrated that the hydrophobic shell can effectively reduce the adsorption amount and desorption activation energy of H₂O on the surface of the catalyst. H₂O generated during the reaction can rapidly desorb from the surface of catalysts without participating in the water–gas shift reaction, which is crucial for regulating CO₂ production. This study examines the interaction between H₂O and catalysts from a microscopic perspective, providing new basic understanding for the design and optimization of catalysts with low CO₂ selectivity.