Highly Active and Dispersed Ni/Al₂O₃ Catalysts for CO Methanation Prepared by the Cation–Anion Double-Hydrolysis Method: Effects of Zr, Fe, and Ce Promoters

Abstract

A highly dispersed nickel catalyst supported on alumina with an NiO loading of 40 wt % has been prepared from Ni­(NO3)2·6H2O and NaAlO2 as precursors through a novel cation–anion double-hydrolysis strategy. The product has been tested for its efficacy in CO methanation. The preparation process can be considered as a time-saving and green synthetic technique that does not require the use of a basic precipitation agent. The resulting Ni/Al2O3 catalyst shows a high dispersion of NiO with small particle size (<5 nm), in spite of the high metal loading. Various promoters, namely Zr, Fe, and Ce, were further added to regulate the catalytic properties of the Ni/Al2O3 catalyst, and 40Ni-5Zr/Al2O3 showed the optimal CO methanation activity. The improved catalytic performance could be mainly due to the high degree of Ni dispersion and the abundance of oxygen vacancies, which enhanced the adsorption and dissociation of CO.

CO2 Reforming of Methane over a Highly Dispersed Ni/Mg–Al–O Catalyst Prepared by a Facile and Green Method

“…Notably, ultrasmall Ni nanoparticles and abundant basic sites were critical structural characteristics of the Ni/Mg–Al–O catalyst, which were endowed by the unique preparation protocols of CADH. According to previous studies on formation mechanisms, − , the Ni 2+ (cations) and AlO 2 – (anions) hydrolyze slowly in separate solutions following eqs and , respectively. Upon the dropwise addition of Ni 2+ solution into AlO 2 – solution, double hydrolysis of Ni 2+ and AlO 2 – proceeds rapidly due to the fast combination between H + and OH – (the overall reaction is described with eq ).…”

“…48,49 Notably, ultrasmall Ni nanoparticles and abundant basic sites were critical structural characteristics of the Ni/Mg−Al− O catalyst, which were endowed by the unique preparation protocols of CADH. According to previous studies on formation mechanisms, [13][14][15]50 − proceeds rapidly due to the fast combination between H + and OH − (the overall reaction is described with eq 3). Such a mutually promoted precipitation process during double hydrolysis ensures uniform blending of various ingredients in the first stage of solid formation, which brings about strong metal−support interactions and eventually leads to ultrasmall Ni nanoparticles.…”

“…Recently, cation–anion double hydrolysis (CADH) has been reported as a facile and green method to synthesize catalysts supported on mesoporous Al 2 O 3 , in which double hydrolysis of cations and anions occurs in a mutually promoted way to form mesoporous mixed oxides. − The inorganic salt of NaAlO 2 serves as both the precipitant agent and the aluminum precursor. Compared with previous methods, CADH possesses prominent advantages.…”

“…The diffraction peaks around 45.0 and 66.5°were much wider than those of pure Al 2 O 3 phases, manifesting the existence of NiAl 2 O 4 phases. 24−26 Relatively weak signals were found for metallic Ni phases (JCPDS No.04-0850) over both investigated catalysts, which may be due to high dispersion, amorphous structure, or limited amount of Ni nanoparticles 13,15.…”

WOx‐Modified Ni Catalyst Supported on Mesoporous Silica with Extra‐Large Mesopores for CO Methanation

“…Therefore, using H 2 produced with renewable energy sources and conversion of coal to methane via the carbon monoxide (CO) methanation reaction, which not only reduces the CO emissions but also meets the market demand for the production of synthetic natural gas (SNG) in China due to the rich coal resource storage, are becoming popular . CO methanation reaction (CO + 3H 2 → CH 4 + H 2 O, Δ H = −206.1 kJ mol −1 ) is a strongly exothermic reaction, which can be conducted in the presence of many metallic catalysts such as Au, Ru, Pd, Co, and Ni. Among them, Ni‐based catalysts are of particular interest for both lab research and industrial applications due to the high catalytic performance and low cost .…”