Effect of nickel on combustion synthesized copper/fumed‐SiO₂ catalyst for selective reduction of CO₂ to CO

In this study, we explore the effect of nickel incorporation in Cu/fumed-SiO₂ catalyst for CO₂ reduction reaction. Two catalysts, Cu and CuNi supported on fumed silica were synthesized using a novel surface restricted combustion synthesis technique, where the combustion reaction takes place on the surface of the inert fumed-SiO₂ support. An active solution consisting of a known amount of metal nitrate precursors and urea (fuel) was impregnated on fumed silica. The catalyst loading was limited to 1 wt% to ensure localized combustions on the surface of fumed-SiO₂ by restricting the combustion energy density. The synthesized catalysts were tested for CO₂ hydrogenation reaction using a tubular packed bed reactor between temperature 50°C and 650°C, where Cu/SiO₂ showed high CO₂ conversion to carbon monoxide, and the addition of Ni further improved the catalytic performance and showed some tendency for methane formation along with CO. Moreover, both the catalysts were highly stable under the reaction conditions and did not show any sign of deactivation for ~42 hours time on stream (TOS). The catalysts were characterized using X-ray diffractometer (XRD), scanning electron microscope/energy dispersive X-ray spectrometer (SEM/EDX), transmission electron microscope (TEM), and the Brunauer-Emmet-Teller (BET) surface area measurement technique to understand their structural properties and to assess the effect of CO₂ conversion reaction. In situ DRIFTS was also used to investigate the reaction pathway followed on the surface of the catalysts.