Insights to the microwave effect in formation and performance promotion of iron-based carbon nanofibrous composites for H2S removal

Abstract

Iron-based carbon nanofibrous composites were synthesized as high-temperature coal gas desulfurization sorbents by electrospinning, pre-oxidation and conventional/microwave carbonizations. Compared with conventional method, microwave carbonization effectively promoted the nucleation and growth of zero-valent iron (ZVI) among nanofibers, which in turn expedited the carbonization process of carbon matrix via the catalytic graphitization. Desulfurization performance evaluations showed that the sorbent carbonized by microwave at 700 °C possessed the highest breakthrough sulfur capacity (3.81 g S 100 g−1 sorbent), which might be attributed to the porous structure and rich content of iron species on the surface of nanofibers. The local high temperature induced by the interaction of microwaves and ZVI imparted the sorbent with porous microstructure. In addition, the rapid and high-temperature carbonization of microwave greatly enhanced the diffusion of Fe to the fiber surface due to the difference in thermal expansion coefficients of Fe and carbon. As a consequence, microwave carbonization involves the advantages of high energy efficiency and structural strengthening effect, suggesting its potential for the preparation of desulfurization sorbent.