Direct synthesis of liquid fuels and aromatics from syngas over mesoporous FeZrOx catalyst mixed with Mo/ferrierite

Abstract

Fischer–Tropsch synthesis (FTS) reaction on the hybrid catalysts containing a highly ordered mesoporous FeZrOx bimetal oxide physically mixed with Mo-modified ferrierite (Mo/HFER) were carried out to directly produce environmentally benign middle distillates and aromatics (BTXs) from syngas. Compared to the pristine FeZrOx itself, the simply mixed hybrid catalyst largely enhanced the selectivity to middle distillates and aromatics (BTXs) through direct CO hydrogenation by preserving its original ordered structures in the forms of partially reduced iron oxides due to their stronger interactions. At an optimal Mo content (~6 wt%) on the HFER frameworks, the hybrid FeZr-Mo(6)/HFER showed the synergistic effects such as higher CO conversion (59.7%) to liquid hydrocarbons (78.4% for C5–C20, 3.7% for C21+ and 5.7% for aromatics including BTXs) with a smaller CO2 formation due to the less accumulation of carbonaceous deposits, optimum hydrophilicity, lower water-gas shift (WGS) reaction activity and larger number of weak acid sites. However, an excessive amount of Mo promoter (>6 wt%) on the acidic HFER surfaces accelerated the formation of the graphitic carbons leading to the decrease of catalytic activity, which were attributed to its excess hydrophobicity and small amounts of acidic sites.