Template Synthesis of Sulfur-Doped Mesoporous Carbon for Efficiently Removing Gas-Phase Elemental Mercury from Flue Gas

Abstract

Sulfur doped mesoporous carbon (SMC) was synthesized by using template method for efficiently removing gas-phase elemental mercury from flue gas. MCM-41 was used as sorbent template, and the mixture of thymol blue (C₂₇H₃₀O₅S) and 2-thiophene ethanol (C₆H₈OS) was screened as co-precursor of carbon and sulfur. The mercury removal performance of the SMC was evaluated by fixed-bed mercury adsorption experiment. Effect of precursor ratio, carbonization temperature, adsorption temperature, and SO₂ on mercury removal was studied. Combining with sorbent characterization, the mercury removal mechanism of the SMC was clarified. The results show that when the ratio of precursor (thymol blue: 2-thiophene ethanol) is 1:6 and the carbonization temperature is set at 900 ℃, the synthetic SMC-900 sorbent is a promising mercury sorbent, which displays excellent mercury removal performance as well as high SO₂ resistance. Decrease of carbonization temperature from 900 ℃ to 700 ℃ significantly reduces the mercury removal performance of SMC due to incomplete carbonization. At 50~150 ℃, the mercury removal rate of SMC-900 is more than 97%, but the higher temperature inhibits its mercury removal. The characterization result shows that the SMC-900 is spherical shape nanoparticle and the BET specific surface area reaches 933.0 m²/g. The mass proportions of carbon (C) and sulfur (S) of SMC-900 are 81.29% and 10.29%, respectively. The sulfur in SMC-900 is in the form of thiophene bond (C-S-C) and oxidized sulfur (C-SOx-C). In the presence of SO₂, the mercury removal product is mainly HgS and a small amount of oxygen-containing functional group is occupied by SO₂.

Keywords: Template Method, Sulfur Doping, Mesoporous Carbon, Elemental Mercury, Removal