Nitrogen-doped carbon nanotube spheres as metal-free catalysts for the partial oxidation of H2S

Nitrogen-doped carbon nanotubes (N-CNTs) with macroscopic shaping were synthesized by a coagulation route using alginate as a coagulating agent and the as-synthesized sample was used as metal-free catalysts in the partial oxidation of H₂S into elemental sulfur. The N-CNT beads display a relatively high desulfurization activity along with a high stability as a function of time on stream. The desulfurization performance of the N-CNT beads was also measured and compared to that of the Fe₂O₃/SiC catalyst. The N-CNT beads display a higher desulfurization activity under the similar reaction conditions with, however, lower sulfur selectivity due to the problem of diffusion of the reactant through the bead porosity.