Comparative Studies of Fischer-Tropsch Synthesis on Iron Catalysts Supported on Al2O3-Cr2O3 (2:1), Multi-Walled Carbon Nanotubes or BEA Zeolite Systems

Mierczynski Mierczynski,Dawid Dawid,Witoska Witoska,Vasilev Vasilev,Chalupka Chalupka,Maniukiewicz Maniukiewicz,Szynkowska Szynkowska

doi:10.3390/catal9070605

Abstract

The main goal of the presented paper is to study the influence of a range of support materials, i.e., multi-walled carbon nanotubes (MWCNTs), Al2O3-Cr2O3 (2:1), zeolite β-H and zeolite β-Na on the physicochemical and catalytic properties in Fischer-Tropsch (F-T) synthesis. All tested Fe catalysts were synthesized using the impregnation method. Their physicochemical properties were extensively investigated using various characterization techniques such as the Temperature-Programmed Reduction of hydrogen (TPR-H2), X-ray diffraction, Temperature-Programmed Desorption of ammonia (TPD-NH3), Temperature-Programmed Desorption of carbon dioxide (TPD-CO2), Fourier transform infrared spectrometry (FTIR), Brunauer Emmett Teller method (BET) and Thermogravimetric Differential Analysis coupled with Mass Spectrometer (TG-DTA-MS). Activity tests were performed in F-T synthesis using a high-pressure fixed bed reactor and a gas mixture of H2 and CO (50% CO and 50% H2). The correlation between the physicochemical properties and reactivity in F-T synthesis was determined. The highest activity was from a 40%Fe/Al2O3-Cr2O3 (2:1) system which exhibited 89.9% of CO conversion and 66.6% selectivity toward liquid products. This catalyst also exhibited the lowest acidity, but the highest quantity of iron carbides on its surface. In addition, in the case of iron catalysts supported on MWCNTs or a binary oxide system, the smallest amount of carbon deposit formed on the surface of the catalyst during the F-T process was confirmed.

Highlights

Fischer-Tropsch synthesis is a promising catalytic route for the environmentally friendly production of fuels from biomass, coal and natural gas [1,2,3,4,5]
The catalytic measurements performed in the hydrogenation process showed that the distribution of the hydrocarbons in the final product depends strongly on the support used for the catalytic system
The results of the reactivity tests showed that the type of hydrocarbons formed in the hydrogenation of CO reaction depended strongly on the catalyst composition

Summary

Introduction

Fischer-Tropsch synthesis is a promising catalytic route for the environmentally friendly production of fuels from biomass, coal and natural gas [1,2,3,4,5]. Metallic catalysts in Fischer-Tropsch synthesis are often supported on oxides, zeolites or binary oxides systems and, more recently, on carbon-based systems such as activated carbon and carbon nanotubes (CNT) [7,8,9]. Carbon nanotubes are exciting due to their unique original chemical, physical, optical and electron properties. Their special structure offers a high surface area and the presence of various defects which offer the possibility to introduce functional groups.

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Conclusion