Impacts of SiC Carrier and Nickel Precursor of NiLa/support Catalysts for CO₂ Selective Hydrogenation to Synthetic Natural Gas (SNG)

Abstract

The porous silicon carbide (β‐SiC) carrier supported nickel‐lanthanum based catalysts (NiLa/SiC) were synthesized via incipient‐wetness impregnation by using two types of nickel salts as the precursor, for the selective hydrogenation of carbon dioxide (CO2+4H2→CH4+2H2O). The alumina supported catalysts were also prepared and tested for comparison. The samples were characterized using TEM, TPR, XRD, SEM, TG‐DTG techniques. Compared to the Al2O3 supported catalysts, the SiC supported catalysts were more resistant to sintering and carbon deposition due to the high thermal conductivity of SiC support. The relative weak metal‐support interaction on Ni nanoparticles supported on SiC carrier resulted in the easy reduction of active species during the activation process. Meanwhile, the performances of the catalysts prepared from nickel acetate were better than those of using nickel nitrate, while enhanced nickel dispersion and better reducibility of the catalyst from nickel acetate werr evidenced by TEM, TPR and XRD results. Catalytic performances exhibited that Ni−Ac‐La/SiC catalyst possessed the higher activity with 89.4 % conversion of CO2 and almost 100 % selectivity to methane with slight deactivation after 3000 min test under reaction conditions.

Enhanced low‐temperature activity for CO2 methanation over NiMgAl/SiC composite catalysts

“…The H 2 ‐TPR results demonstrated that SiC substrate effectively tuned the metal‐support interactions between Ni and MgAl support. The absence of reduction peak above 700 °C over the NiMgAl/SiC catalyst should be related to the chemical inertness of SiC substrate and the partial covering of SiC with MgAl layers . Similar phenomena have been reported on the Co/Al 2 O 3 /SiC system with the Co/Al 2 O 3 catalyst as a reference …”

“…The absence of reduction peak above 700 ∘ C over the NiMgAl/SiC catalyst should be related to the chemical inertness of SiC substrate and the partial covering of SiC with MgAl layers. 35,36 Similar phenomena have been reported on the Co/Al 2 O 3 /SiC system with the Co/Al 2 O 3 catalyst as a reference. 36 The metal-support interactions would influence the reducibility of the catalysts accordingly.…”

“…Therefore, the slight deactivation should be caused by the mild metal sintering. The high heat conductivity of SiC would facilitate heat dissipation of the catalyst in CO 2 methanation, alleviating metal sintering and thus preventing carbon deposition on the NiMgAl/SiC catalyst …”

CO2 methanation under dynamic operational mode using nickel nanoparticles decorated carbon felt (Ni/OCF) combined with inductive heating

“…TiO 2 , SiO 2 , Al 2 O 3 , CeO 2 , MgO and ZrO 2 ). [31][32][33][34][35][36][37][38][39][40] It is a highly exothermic process (H = -165 kJ/mol) and thus, 5 thermal conductive supports (carbon nanotubes, graphene, and silicon carbide just to mention a few) [41][42][43][44][45] are generally recommended in order to prevent as much as possible the generation of local temperature gradients (hot spots) inside the catalyst bed during the process. Indeed, the generation of "hot spots" inside the catalyst can be largely detrimental both in terms of catalyst life-time and performance of the methanation process.…”

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

“…Chu et al pointed out the higher reducibility of Ni-oxide NPs and anticoking properties of their bimetallic Ni–La methanation catalysts prepared on SiC networks compared to their γ-Al 2 O 3 -based counterparts . These authors argued on the importance of weaker metal–support interactions between Ni NPs and the SiC carrier.…”