Abstract
Two different groups of CoMn catalysts derived from hydrotalcite-like precursors were prepared through the co-precipitation method, and their performance in the direct production of gasoline and jet fuel range hydrocarbons through Fischer–Tropsch (FT) synthesis was evaluated in a batch autoclave reactor at 240 °C and 7 MPa and H2/CO of 2. The physicochemical properties of the prepared catalysts were investigated and characterized using different characterization techniques. Catalyst performance was significantly affected by the catalyst preparation method. The crystalline phase of the catalyst prepared using KOH contained Co3O4 and some Co2MnO4.5 spinels, with a lower reducibility and catalytic activity than cobalt oxide. The available cobalt active sites are responsible for the chain growth, and the accessible acid sites are responsible for the cracking and isomerization. The catalysts prepared using KOH + K2CO3 mixture as a precipitant agent exhibited a high selectivity of 51–61% for gasoline (C5–C10) and 30–50% for jet fuel (C8–C16) range hydrocarbons compared with catalysts precipitated by KOH. The CoMn-HTC-III catalyst with the highest number of available acid sites showed the highest selectivity to C5–C10 hydrocarbons, which demonstrates that a high Brønsted acidity leads to the high degree of cracking of FT products. The CO conversion did not significantly change, and it was around 35–39% for all catalysts. Owing to the poor activity in the water-gas shift reaction, CO2 formation was less than 2% in all the catalysts.
Highlights
The impending depletion of fossil fuel sources and the growing demand for energy resources because of increasing population and economic development have led to new approaches to the production of renewable liquid fuels
The thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) curves for the CoMn catalysts derived from hydrotalcite-like precursors (CoMn-HTC catalysts) (Figure 2) exhibited several phases of weight loss because of the thermal decomposition of catalysts, and the same behavior was observed in the DTG curves
The peaks at 100–260 ◦ C were attributed to the evaporation of physically adsorbed water and interpolated water molecules associated with the dried samples. This result is in good agreement with the mass spectroscopy results, showing that water was released at this temperature range, and weight loss mainly occurred at this range
Summary
The impending depletion of fossil fuel sources and the growing demand for energy resources because of increasing population and economic development have led to new approaches to the production of renewable liquid fuels. Carbonaceous resources are transformed into syngas (H2 + CO) through reforming, gasification, or partial oxidation and converted to a wide range of hydrocarbons. These hydrocarbons are refined to produce final products, including liquefied petroleum gas, gasoline, jet fuel, distillate, diesel, and wax [2].
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