B-Ni/MgAl2O4 catalyzed dry reforming of methane: The role of boron to resist the formation of graphitic carbon

The present contribution reports a single-step synthesis of B(x)-Ni/MgAl2O4 (where x = 1%, 3%, and 5% wt.%) via the NaBH4 reduction for dry reforming of methane (DRM) and investigates the effect of B promotion. Characterization (ICP-OES, XRD, H2-TPR, XPS, HR-TEM with EDS and HAADF) results suggested B incorporation facilitates the formation of Ni0 and Ni-B species and smaller Ni particle size (∼7 nm) compared to unpromoted catalyst. The results of the DRM reaction indicated that ∼ 2.8 wt% B-containing catalyst (B(3)-Ni/MgAl2O4) exhibited maximum activity and minimum decline in conversion (%) for both reactants (CH4 and CO2). The Turnover frequency (TOFCH4) observed for the B(3)-Ni/MgAl2O4 is ∼ 2.6 times higher than the non-B catalyst. The investigation of spent catalysts confirms the insignificant deactivation due to the absence of graphitic carbon. The carbon formation is (∼11.2 times) lesser for B(3)-Ni/MgAl2O4 than for the non-B catalyst. The enhanced activity and low carbon deposition for B (∼2.8 wt%) containing catalyst attributed to the occupancy of B in octahedral sites of the Ni-sub surface, which restricts the crystalline growth leading to a smaller Ni particle size, stabilize the metallic state of Ni, and affect the Ni-C interaction during DRM.