Nanostructured Carbon Material Effect on the Synthesis of Carbon-Supported Molybdenum Carbide Catalysts for Guaiacol Hydrodeoxygenation

Abstract

The impact of using different nanostructured carbon materials (carbon nanofibers, carbon nanotubes, graphene oxide and activated carbon) as a support for Mo2C-based catalysts on the hydrodeoxygenation (HDO) of guaiacol was studied. To optimise the catalyst preparation by carbothermal hydrogen reduction (CHR), a thermogravimetric study was conducted to select the optimum CHR temperature for each carbon material, considering both the crystal size of the resulting β-Mo2C particles and the extent of the support gasification. Subsequently, catalysts were prepared in a fixed bed reactor at the optimum temperature. Catalyst characterization evidenced the differences in the catalyst morphology as compared to those prepared in the thermogravimetric study. The HDO results demonstrated that the carbon nanofiber-based catalyst was the one with the best catalytic performance. This behaviour was attributed to the high thermal stability of this support, which prevented its gasification and promoted a good evolution of the crystal size of Mo species. This catalyst exhibited well-dispersed β-Mo2C nanoparticles of ca. 11 nm. On the contrary, the other supports suffered from severe gasification (60–70% wt. loss), which resulted in poorer HDO efficiency catalysts regardless of the β-Mo2C crystal size. This exhibited the importance of the carbon support stability in Mo2C-based catalysts prepared by CHR.

Interfacial engineering and chemical reconstruction of Mo/Mo2C@CoO@NC heterostructure for promoting oxygen evolution reaction

“…42-1120), 31 Mo 2 C (JCPDS No. 35-0787), 32 and MoC 2 O 4 33 species can be detected, which is due to the carbothermic reduction reaction and the reaction of carbon with MoO 3 , respectively. The formation of the CoO phase originates from the carbonization of ZIF-67.…”

Supported transition metal (Mo, W) carbide and nitride catalysts for lignin hydrodeoxygenation: interplay of supports, structure, and catalysis

“…Under the same conditions, the active order was Mo 2 C/CNF > Mo 2 C/AC > Mo 2 C/RGO > Mo 2 C/CNT (Table 2, entries 4–7). 69 As seen from the result of XPS and N 2 physisorption, the highest HDO activity of Mo 2 C/CNF is associated with not only the highest concentration of Mo 2+ and Mo δ + (2 < δ < 3) species on the catalyst surface but also the dispersion of active sites into meso- and macropores. This is inseparable from the higher thermal stability of CNF.…”

“…70 In the case of Mo 2 C/AC, the lower surface active Mo contents and microporous nature of AC may account for the lower catalytic activity as compared to Mo 2 C/CNF, despite the larger amount of Mo. 69 The H 3 PO 4 activated biochar is more efficient for guaiacol conversion than commercial AC (Table 2, entries 9 and 10) 72 due to the acidic groups introduced into the surface of biochar by H 3 PO 4 acidification, such as hydroxyl and carboxyl groups, that promoted the conversion of guaiacol into phenol. However, these acidic groups seem to be not stable for continuous use as a catalyst.…”