Cu dispersed TiO2 catalyst for direct hydrogenation of carbon dioxide into formic acid

Abstract

The exponential increase in CO2 emission enforced the discovery of alternative methods to curb excessive atmospheric CO2. In the present manuscript, nano-crystalline copper disperced TiO2 (CuOx-TiO2) catalyst has been explored for the direct hydrogenation of CO2 into formic acid (FA) under hydrothermal condition. Series of Cu based catalysts were synthesized via a simple co-precipitation method and tested for CO2 hydrogenation. Of the tested catalyst, CuOx-TiO2 showed the highest TON (turnover number) 6.62 for FA under non-stringent reaction conditions (40 bar, 200 °C). The addition of base (both organic/ inorganic) showed significant improvement in CO2 reduction. Inorganic bases showed a profound effect to obtain a higher yield of FA as compared to organic bases. The process intensification study was conducted for the influence of temperature, base, concentration of base, pressure, catalyst loading, and reaction time on FA production. The physicochemical properties of the synthesized catalyst were studied by using XRD, ATR-FTIR, BET, FEG-SEM, EDX, and ICP-OES analysis. Catalyst recyclability study showed the gradual drop in TON and TOF for five cycles but the easy regeneration process reboots the catalytic activity. The plausible reaction mechanism for direct hydrogenation of CO2 to FA has also been proposed.