Enhancing Hydrophobicity and Sulfur Tolerance for CO2 Adsorption by Constructing Polar Molecular Fences via Silylation

Abstract

Adsorption of CO2 from blast furnace gas (BFG) faces competitive adsorption of H2O and poisoning by H2S. Suppression of H2O and a small amount of H2S adsorption preserving CO2 adsorption, was required for zeolite-based pressure swing adsorption (PSA) technology. The zeolite-based composite was explored for CO2 adsorption, which was fabricated by Y zeolite functionalized with short-chain (MTCS) and long-chain (BTS) silanes. Under static CO2 adsorption conditions, CO2 absorption capacity of Y, MTCS-Y, and BTS-Y were 100.39, 100.81, and 104.23 cm3·g–1, respectively, and H2O adsorption of silanized zeolite was reduced. Multicomponent competitive adsorption (CO2/H2O/H2S) showed that the H2O and H2S breakthrough times of zeolite-modified long-chain silane were greatly shortened, suggesting better hydrophobicity and inhibiting H2S adsorption. After H2S exposure, in comparison to Y zeolite, the total sulfur deposition on MTCS-Y and BTS-Y declined by 48.75% and 71.25%, respectively. MTCS-Y showed excellent hydrophobic stability and sulfur resistance, as evidenced by the preservation of its surface contact angle and the retention of 96.5% of its original CO2 adsorption capacity. Electrostatic potential calculation (ESP), in situ FTIR, and breakthrough experiments revealed that H2O and H2S adsorption of silanized zeolite was inhibited by the Y hydrophobic layer physical blocking and interface polarity adjustment. Silanized Y zeolites significantly inhibited the adsorption of H2O and H2S for CO2 adsorption in BFG conditions.