Lewis Acid Sites Stabilized Nickel Catalysts for Dry (CO₂) Reforming of Methane

Abstract

Strong Lewis acid species [Al–F] were synthesized on a series of Al2O3‐supported Ni catalysts modified with (0, 1, 5, and 10 wt.%) of KF to investigate the electronic and anchoring effect of [Al–F] on Ni catalysts in terms of catalytic activity, stability, and carbon resistance during dry reforming of methane (DRM) reaction. With the aids of XRD analysis, X‐ray photoelectron spectroscopy, H2 temperature‐programmed reduction, and in situ diffuse reflectance infrared Fourier transform spectroscopy analyses, it was found that the activity and stability of KF‐modified catalysts in the reaction was directly associated to the presence of [Al–F] sites. The [Al–F] Lewis acid sites not only stabilized the metal Ni from high‐temperature sintering after reaction of 200 h through an enhanced metal–support interaction, but also reduced the electron density of Ni metal, which alleviated the fast decomposition of CH4 and subsequent carbon deposition on catalysts. Balancing the rates for CH4 dissociation and carbon removal would be promising steps in the design of active and stable Ni‐based catalysts.

Sandwich‐Like Silica@Ni@Silica Multicore–Shell Catalyst for the Low‐Temperature Dry Reforming of Methane: Confinement Effect Against Carbon Formation

“…X‐ray photoelectron spectroscopy (XPS) was performed, and the results are presented in Figure . For the reduced NiPS, besides the peak at a binding energy (BE) of 852.6 eV for Ni 0 , there is another peak at BE=855.6 eV, which is assigned to Ni 2+ species in a 1:1 ratio in the PS phase . Therefore, even after H 2 reduction at 800 °C for 1 h, PS remains in the structure.…”

Fibrous spherical Ni‐M/ZSM‐5 (M: Mg, Ca, Ta, Ga) catalysts for methane dry reforming: The interplay between surface acidity‐basicity and coking resistance

“…The addition of Ta influenced Ni‐support interaction, and the medium‐weak acid sites serves as anchoring sites for Ni particles stabilization. According to previous report, medium acid sites of Ni/KF‐Al 2 O 3 could effectively inhibit coke deposition and sintering due to improved metal‐support interaction . Hence, carbon deposition was less on Ni‐Ta/FZSM‐5, which supports its stable performance in DRM as discussed earlier.…”

“…In our current case, after addition of Ta, the strong acid sites were engulfed; thus, the number of strong acid sites decreased. Accordingly, a new type of acid site was observed around 332°C which could be regarded as medium acid sites . Essentially, medium‐weak acid sites could facilitate formation of distinct adsorptive sites that stabilise metal nanoparticles and aid redispersion of Ni particles.…”

“…The fibrous morphology not only offer high surface area but also reinforced confinement of Ni particles, exhibiting remarkable performance much better than conventional SiO 2 support. In addition, the dispersion and stabilisation of active metals in reactions where coking and sintering are prone can also be controlled by the acid sites, especially Lewis acid sites (LAS) . The LAS serves as anchoring sites for stabilisation of active metals in reactions such as CO methanation, CO oxidation and hydrazine decomposition .…”

“…The LAS serves as anchoring sites for stabilisation of active metals in reactions such as CO methanation, CO oxidation and hydrazine decomposition . Further, Ni et al reported that LAS‐stabilised Ni metal from high temperature sintering due to enhanced metal‐support interaction. Thus, structuring of zeolite support can enhance the catalytic properties.…”