Removing mercury from flue gas by sulfur-doped zeolite-templated carbon: Synthesize and adsorption mechanism

Abstract

Elemental mercury is harmful to humanity and the ecological environment. It is a simple and feasible method to capture elemental mercury by carbon-based adsorbents. The purpose of this work is to develop zeolite-templated carbon with and without sulfur (ZTC and S-doped ZTC) and to explore their mercury adsorption performance. ZTC and S-doped ZTC were synthesized by chemical vapor deposition (CVD) method and their mercury adsorption performance were tested at 30 and 150 °C. Among all ZTC samples, BEA-ZTC-HS exhibited highest mercury removal efficiency (MRE) whose initial value was 99.99% (150 °C) and 97.39% (30 °C) and decreased to 96.63% and 89.15% after one hour mercury adsorption. The physical and chemical properties of the ZTC samples were characterized by various methods to explain the high MRE of BEA-ZTC-HS. The experimental results shown that BEA-ZTC-HS replicated the crystal structure of BEA zeolite faithfully and exhibited regular microporous structure and doesn’t have obvious elemental sulfur whose existence could block the micropores in ZTC. This was helpful to the mass transfer of Hg0 in ZTC. Moreover, the chemical properties of BEA-ZTC-HS shown that the introduced sulfur were mainly bonded to the carbon framework of ZTC in the form of thiophene, sulfone, sulfoxide and sulfonic acid. Those sulfur-containing functional groups provided main active sites for mercury capture and exhibited higher activity at 150 °C. Finally, Density Functional Theory (DFT) was used to reveal the adsorption mechanism of ZTC and S-doped ZTC on Hg0. Due to its good properties of regeneration, higher MRE, good thermal stability and low cost, BEA-ZTC-HS has a wide prospect for industrial application in the wide temperature ranges compared to the activated carbon injection technology.