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 tolerance. Decrease of carbonization temperature from 900 ℃ to 700 ℃ significantly reduces the mercury removal performance of SMC due to the incomplete carbonization of precursor. At 50–150 ℃, the mercury removal rate of SMC-900 is more than 97%, but a higher temperature inhibits its mercury removal capacity. 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 main mercury removal product is HgS because the oxygen-containing functional group is occupied by SO2.