Insight of boron induced single-step synthesis of short-chain olefins from bio-derived syngas

Abstract

Syngas derived from Biomass appears to be an excellent and renewable building block in recent times for the synthesis of chemicals and fuels. Modified iron nanoparticles have been synthesised through Boron infusion in a facile one-step approach and utilised as a catalyst for direct and selective conversion of Bio-derived syngas to light olefins (FTO). Compared to the pristine iron nanoparticles, the boron-infused materials exhibit relatively lower CO conversion and higher selectivity towards short-chain olefins. Moreover, the newly developed materials demonstrate high stability and excellent resistivity towards deactivation without any sintering and agglomeration under applied reaction conditions. An in-situ diffuse reflectance FTIR (DRIFTS) study was conducted, followed by a computational study to understand the mechanistic insight. The catalysts show maximum C2-C4 olefins selectivity up to 66% at 340 °C, 5 bar, H2/CO = 1 and 3000 h−1 with iron time yield to hydrocarbons, termed as FTY at 19–22 µmolCO/(gFe.s). Doping of boron in synthesising nano-iron oxides helped in controlling the CO conversion activity and improving the yield of olefins. DRIFTS and theoretical studies for CO interaction with these catalytic materials were performed to illustrate the promotional effect imparted by boron. The decrease in the CO adsorption extent and lowering of CO binding energy to active iron carbide phase demonstrate the role of boron in the enhancement of stability of catalyst for an extended period of run in the direct conversion of Bio-derived syngas to light olefins. HRTEM images show that the boron-doped iron nanoparticles are in a finely dispersed state which is retained even after prolonged activity studies.