Enhancement of hydrothermal synthesis of FDU-12-derived nickel phyllosilicate using double accelerators of ammonium fluoride and urea for CO2 methanation

Nickel phyllosilicate materials were usually prepared by the hydrothermal method under severe conditions with high hydrothermal temperature and long hydrothermal time. In order to obtain Ni-phyllosilicate under mild hydrothermal conditions, a modified hydrothermal method assisted by double accelerators of ammonium fluoride and urea was proposed in this work. The N/F-A(100)-12 catalyst was prepared by the modified hydrothermal method at 100 degrees C for 12 h with similar Ni content and morphology as N/F-H-220-48 prepared by the conventional hydrothermal method at 220 degrees C for 48 h. The improvement derived from that ammonium fluoride accelerated the etching of FDU-12 to form the intermediate of H4SiO4, and urea could facilitate the formation of Ni(OH)(2), resulting in the quick formation of Ni-phyllosilicate under mild conditions. N/F-A(100)-12 exhibited high TOFCO2 (220 degrees C) value of 3.05 x 10(-3) s(-1) and low activation energy of 96.5 kJ mol(-1) for CO2 methanation due to the small Ni particle size and enhanced CO2 and H-2 adsorption property. In addition, N/F-A(100)-12 also displayed high long-term stability and anti-sintering property. In all, the modified hydrothermal method was highly efficient to synthesize Ni-phyllosilicate material under mild hydrothermal conditions.