FeCu/SiO2 catalysts prepared by autocombustion method for fischer-tropsch synthesis

Abstract

The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis (FTS) without a reduction step. The effect of different citric acid (CA):iron nitrate (N) molar ratios (CA:N), acid types and SiO2 supports on the FTS performance of catalysts were investigated. The CA:N had an important influence on the formation of iron active phases (FexC) and FTS activity. Increasing the CA:N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA:N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst (CA:N molar ratio = 0.1) achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction. The catalyst prepared using CA and Q-50 type of SiO2 gave a maximum CO conversion when compared with other catalysts. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step for FTS.