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

Influence of Highly Stable Ni2+ Species in Ni Phyllosilicate Catalysts on Selective Hydrogenation of Furfural to Furfuryl Alcohol

“…They reported that ammonium fluoride and urea can be an efficient accelerator of the formation of H 4 SiO 4 and Ni(OH) 2 , respectively, which are essential intermediates for the formation of nickel phyllosilicate. Nickel phyllosilicate could be formed under mild hydrothermal conditions at 100 °C for 12 h by double accelerators of ammonium fluoride and urea, 1 which has a similar morphology and nickel content with a conventional hydrothermal method at 220 °C for 48 h. Although this modified hydrothermal method can improve hydrothermal conditions, there are still some limitations of complicated operation procedures and too low hydrothermal conditions that provide a low nickel content and small amount of nickel phyllosilicate formation. 26 Moreover, the preparation of nickel phyllosilicate usually consists of two major steps: step (1) is the silica material synthesis and step (2) is the nickel phyllosilicate formation via the reaction of a silica material and nickel precursor.…”

“…Nickel is one of the most frequently used metals in a wide variety of industrial manufacturing. Silica-supported nickel catalysts (Ni/SiO 2 ) are used extensively in catalytic reactions due to their low cost, high specific surface area, easy functionalization, and controllable morphology/adjustable pore structures. − However, Ni/SiO 2 usually suffers from a weak interaction between nickel species and silica supports, which is a significant drawback that can cause leaching of nickel species during a liquid phase reaction as well as agglomeration and sintering of nickel under a high thermal treatment and reaction process, leading to low catalytic activity, deactivation of catalyst, and poor stability. Several efficient strategies have been reported to improve nickel dispersion and enhance the metal–support interaction such as the addition of various promoters such as La 2 O 3 and V 2 O 5 , the formation perovskite and hydrotalcite structures, , the modification of the support and developed preparation methods to enhance the metal–support interaction and inhibit the catalyst agglomeration such as molecular layer deposition, and the construction of nickel-based catalysts with a confinement effect like mesostructured cellular foam .…”

“…Generally, nickel phyllosilicates with different crystal structures can be synthesized via various methods including hydrothermal methods, ,− ammonia evaporation methods, − deposition–precipitation methods, , and sol–gel methods through the reaction between a nickel precursor and silica materials. Among which, the hydrothermal method has been employed for preparation of nickel phyllosilicate catalysts due to high crystallinity, handy experimental operation, environmental friendliness, and uniform dispersion of nickel phyllosilicate.…”

Unveiling the Roles of Precursor Structure and Controlled Sintering on Ni-Phyllosilicate-Derived Catalysts for Low-Temperature Methane Decomposition

“…A more controlled version of this phenomenon was achieved by adding NH 4 F to the hydrothermal mixture while retaining the original milder conditions ( 10Ni – SiO 2 -UF ). NH 4 F greatly accelerates the dissolution of SiO 2 into Si­(OH) 4 through the action of HF produced in situ, , thereby promoting free NiPS growth (which consumes dissolved silica) over surface NiPS growth (which consumes surface silanol groups). Hence, the resulting NiPS lamellae do not interact strongly with the Stöber silica nanospheres, instead encapsulating them and filling interparticle voids in a unique and hierarchical walnut-like morphology , (Figure c,d).…”

“…NH 4 F greatly accelerates the dissolution of SiO 2 into Si­(OH) 4 through the action of HF produced in situ, , thereby promoting free NiPS growth (which consumes dissolved silica) over surface NiPS growth (which consumes surface silanol groups). Hence, the resulting NiPS lamellae do not interact strongly with the Stöber silica nanospheres, instead encapsulating them and filling interparticle voids in a unique and hierarchical walnut-like morphology , (Figure c,d). This morphology is independent of the nickel loading, which changes only the coverage of the NiPS layers over the underlying silica spheres (Figure S4).…”