Methane aromatization study on M-Mo2C/HZSM-5 (M = Ce or Pd or Nb) nano materials

The aim of this work is to understand the influence of second metals (M = Ce or Pd or Nb) on Mo 2 C active phase reduction into metallic molybdenum and on surface MoO x species of M-Mo 2 C/HZSM-5 catalysts studied for methane dehydroaromatization at 700 °C with GHSV 1800 mL. g cat −1 . h −1 . The fresh and spent catalysts were characterized by using ATR-FTIR, HRTEM/STEM, BET surface area, XRD, TPO, NH 3 -TPD-mass, XPS and H 2 -TPR techniques. Essentially, the highest benzene yield of 8.4% on Pd–Mo 2 C/HZSM-5 catalyst for 10 h of continuous operation was associated with limited Mo 2 C active phase reduction into metallic molybdenum at Pd–Mo proximity via Pd 2+ to Pd 0 step and promoted coke burning through reduced carbon deposits formation. Further, the surface reduction of CeO 2 to Ce 2 O 3 decreased the methane conversion due to sluggish MoO x species transformation to Mo 2 C active phase. On the other side, Nb 2 O 5 primarily reduced into NbO 2 /NbO resulted in surface MoO x species and external surface Mo 2 C particles eventually produced superior coke via CH 4 decomposition on Nb–Mo 2 C/HZSM-5 catalyst. The decreasing order of benzene yield after 10 h of reaction at 700 °C as follows: Pd–Mo 2 C/HZSM-5 (8.4%) > Mo 2 C/HZSM-5 (7.4%) > Nb–Mo 2 C/HZSM-5 (5.8%) > Ce–Mo 2 C/HZSM-5 (5.2%).