Nickel
phyllosilicate materials were usually prepared by the conventional
hydrothermal method under severe conditions and ammonia evaporation
method with unavoidable ammonia emission. To address these problems,
a versatile double-accelerator method was proposed in this work, which
could successfully synthesize nickel phyllosilicates through the hydrothermal
treatment of silica and nickel nitrate at a quite low temperature
of 40 °C or in an open system at 80 °C without autogenous
pressure assisted by ammonium fluoride (NH4F) and urea.
NH4F could accelerate the etching of silica to form the
intermediate H4SiO4, and urea could facilitate
the formation of a Ni(OH)2 intermediate, resulting in the
quick formation of Ni-phyllosilicates. In addition, this method exhibited
high universality to prepare various metal (Ni, Co, and Cu) phyllosilicates,
and both silica materials and sodium metasilicate could be the potential
silicon-containing precursors to prepare Ni-phyllosilicates. Furthermore,
the sintered Ni/SiO2 catalyst could also be regenerated
after in situ acid pickling and double-accelerator
synthesis without decline of catalytic activity. The optimal Ni-phyllosilicate
catalyst (N/D-120-12) prepared by the double-accelerator method exhibited
a high CO2 conversion of 78.4% and a CH4 yield
of 74.5% at 400 °C, which also obtained a low E
a of 63.93 kJ·mol–1 and a high
TOFCO2
(160 °C) of 3.1 × 10–2 s–1 for CO2 methanation. In
situ DRIFTS results demonstrated that the presence of more
m-HCOO– species on N/D-120-12 resulted in its high catalytic
performance. Moreover, N/D-120-12 also exhibited high long-term and
hydrothermal stability with an excellent anti-sintering property.
A series of MoOx doped Ni/3D-SBA-15 catalysts with a three-dimensional network structure were prepared by an impregnation method using different solvents for CO methanation.
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