1 research outputs found
Interface of Ni-MgCr<sub>2</sub>O<sub>4</sub> Spinel Promotes the Autothermal Reforming of Acetic Acid through Accelerated Oxidation of Carbon-Containing Intermediate Species
Autothermal
reforming (ATR) is an effective route for
hydrogen
production from acetic acid (HAc) derived from biomass. Ni-based catalysts
are promising candidates for ATR due to their high activity, but coke
formation hinders their practical application. To tackle this issue,
a series of Ni-Mg-Cr catalysts with supports of Cr2O3 or MgCr2O4 were prepared by the sol–gel
method and evaluated in ATR. The results indicated that as compared
to the Ni-Cr2O3 catalyst, the Ni0.25Mg0.75CrO3.5±δ catalyst with MgCr2O4 support presented higher catalytic performance:
the conversion rate of acetic acid was stable near 100%, with hydrogen
yield reaching 2.64 mol-H2/mol-HAc during a 40 h ATR test,
while there was no obvious coking. It was found that Mg modification
was prone to constituting a stable MgCr2O4 spinel
support with a high specific surface area for adsorption and transformation
of HAc; however, for catalysts with excessive Mg addition, namely,
Ni0.43Mg2.56CrO4.5±δ and
Ni0.69Mg5.31CrO7.5±δ,
low reactivity was found and was linked to constraining of Ni from
the solid solution of Mg(Ni)O. Density functional theory (DFT) calculations
reveal that during the ATR process, Ni4-MgCr2O4 presents a low energy barrier for the overall transformation
path and a high stabilization of reaction intermediates; furthermore,
as compared to Ni4-Cr2O3, oxidation
of C* species by O* and OH* is significantly accelerated on Ni4-MgCr2O4 due to the considerably decreased
energy barriers, thus eliminating carbon deposition and improving
catalytic activity