Dual-template approach to designing nitrogen functionalized, hierarchical porous carbons for efficiently selective capture and separation of SO2

Abstract

As the typically corrosive and toxic waste gas, sulfur dioxide (SO2) is derived from many industrial processes, its efficient elimination shows great significance for flue gas desulfurization. Herein, a class of hierarchically porous carbons with large BET surface areas (∼1192 m2/g), tunable nanoporosity and high-concentrated nitrogen base sites (6.5 at%) were developed, which were applied for selective capture and separation of sulfur dioxide via enhanced base-acid interaction. The nitrogen functionalized, porous carbons were prepared from a new dual-template route, which was realized from carbonization of a mixture containing zinc gluconate and urea (DT-NPC-xs, where x stands for the ratio of urea to zinc gluconate). In this process, the evaporation of zinc site at high temperature results in formation of abundant microporosity; while the decomposition of urea releases large amount of gas templates and nitrogen dopants, which create tunable meso-macroporosity and versatile nitrogen base sites in DT-NPC-x. The synthesized DT-NPC-xs show SO2 capacity as high as 11.8 mmol/g at 25 °C and 1.0 bar, and the SO2/N2 (0.1/0.9) and SO2/CO2 (0.1/0.9) IAST selectivities were up to 198.7 and 21.5. Breakthrough tests demonstrate the superior elimination of trace SO2 (∼2150 min/g) from ternary mixed gas (SO2/CO2/N2 = 0.6/15/84.4). The overall performance of DT-NPC-3 in SO2 adsorption and separation were superior to many reported adsorbents (e.g. activated carbon, g-C3N4) applied in the field.