Highly uniform molybdenum oxide loaded N-CNT as a remarkably active and selective nanocatalyst for H₂S selective...

Selective oxidation of H₂S to elemental sulfur is a low cost and highly efficient process for sulfur removal from H₂S-containing hydrocarbon streams in medium scale (i.e. 0.2-10 ton sulfur/day) for environmental protection and prevention of emitting toxic gases to the atmosphere. In this research, in order to prepare a highly active and selective nanocatalyst for selective oxidation of hydrogen sulfide, for the first time, molybdenum oxides were loaded uniformly over nitrogen- doped carbon nanotubes through incipient wetness impregnation. Different metal loadings including 5, 10, and 15 wt% Mo were considered in the synthesis procedure to achieve the optimized performance and provide complete environmental protection. The Mox/N-CNT nanocatalysts were thoroughly characterized via TEM, FE-SEM, XPS, N₂ adsorption/desorption, and XRD techniques. The characterization methods confirmed that the Mo oxides nanoparticles were successfully distributed over the N-CNT support uniformly in nanoscale in which there was no sign of agglomeration. The catalytic experiments on Mox/N-CNT were performed in temperature range of 190-230 °C in which the feed gas was composed of 3000 ppm H₂S and 1500 ppm O₂. The results showed that the Mox/N-CNT samples were highly active at all considered temperatures providing the H₂S conversion of almost 100% from which almost no H₂S was emitted. Furthermore, by loading the Mo oxide over the N-CNT support, selectivity toward elemental sulfur was increased significantly at high temperatures (i.e. above 190 °C) suggesting that the progress of side reactions on the nanocatalyst has been minimized. The best result was obtained with the sample containing 15 wt% Mo at 230 °C providing the H₂S conversion of 100% and selectivity of 89.7%. According to these results, Mo oxide/N-CNT is introduced as a potential candidate for catalytic H₂S removal processes toward environmental protection in industrial plants.