Conversion of CO 2 and small alkanes to platform chemicals over Mo 2 C-based catalysts

The performance of Mo 2 C-based catalysts in CO 2 assisted oxidative dehydrogenation (CO 2 -ODH) of ethane was evaluated. Mo 2 C on SiO 2 was synthesized via three different techniques: wet impregnation (WI), hybrid nanocrystal technique (HNC) and sol–gel method (SG) and exposed to the same carburization conditions. In terms of characteristic properties, the allotrope composition was the most affected, with the SG sample containing MoO x C y and the WI and HNC samples containing β-Mo 2 C. The two different allotropes were suggested to follow different reaction pathways, leading to small differences in the catalytic performance. However, overall, all three catalysts showed a decrease in activity (below 6%) and an increase in C 2 H 4 selectivity (from 60 to 80 C%) with time on stream (TOS). The deactivation mechanism was suggested to be mainly due to oxidation of the carbide to MoO x and carbon deposition. Mo 2 C was also supported on various metal oxide materials via the wet impregnation technique. Mo 2 C supported on Al 2 O 3 and ZrO 2 increased initial activity (about 8% C 2 H 6 conversion) but a faster deactivation with TOS was observed. Mo 2 C/Ga 2 O 3 favoured the direct dehydrogenation reaction achieving high C 2 H 4 selectivities (above 80 C%), but deactivation with TOS due to carbon deposition was significant. Mo 2 C supported on CeO 2 and TiO 2 had lower activity (about 3% C 2 H 6 conversion). Oxidation to MoO 2 and carbon deposition is again suggested to be the main deactivation mechanism. H 2 co-feeding, on Mo 2 C/SiO 2 and Mo 2 C/ZrO 2 , increased the stability of the catalysts but C 2 H 4 yield was affected (from 5 to 2%). At 17 vol% H 2 co-feeding, Mo 2 C/ZrO 2 showed promising catalyst stability over a 20 h period, paralleled by a stable C 2 H 4 yield.