Decomposition of formic acid over Ni-containing SiO2 catalysts synthesized by various one-pot synthesis routes

In this study SiO 2 supported catalysts with different nickel amounts [5Ni–SiO 2 (P123), 2,5Ni–SiO 2 (P123), 5Ni–SiO 2 (NH 3 -CA), 5Ni–SiO 2 (Tw80–NaF) and 5Ni–SiO 2 (Tw80)] were synthesized with four different one-pot synthesis routes. These catalysts were characterized by XRD, ATR/FT–IR, SEM–EDS, N 2 adsorption–desorption analysis and tested for hydrogen production from catalytic gas-phase decomposition of formic acid. XRD and ATR/FT-IR results confirmed the presence of a metallic Ni phase in the catalysts. It was seen that the catalysts synthesized with surfactant Pluronic 123 (P123) exhibited the highest surface area. The N 2 adsorption–desorption isotherms of the catalysts other than 5Ni–SiO 2 (Tw80–NaF) were consistent with Type IV according to the IUPAC classification. Pore structure deterioration was observed in catalysts synthesized using Tw80–NaF and synthesized by the surfactant-free one-pot method [5Ni–SiO 2 (NH 3 -CA)]. The highest H 2 selectivity was observed at 350 °C for empty reactor and it was decided to conduct the activity test studies of the catalysts at this temperature. All catalysts exhibited complete formic acid conversion at 350 °C. The Lewis acidity order of the catalysts was found to be 2.5Ni–SiO 2 (P123) > 5Ni–SiO 2 (Tw80) > 5Ni–SiO 2 (NH 3 -CA) > 5Ni–SiO 2 (P123). The highest H 2 concentration and selectivity were obtained with the 5Ni–SiO 2 (P123) catalyst. As a result, it was determined that the acidic-basic property of the catalyst may be more dominant than the other properties (pore properties, surface area, Ni crystallite size) on the catalytic activity in hydrogen production from formic acid.