The effect of microwave heating on manganese promoted iron based Fischer-Tropsch catalysts
| dc.contributor.author | Mohiuddin, Ebrahim | |
| dc.date.accessioned | 2012-01-18T10:28:28Z | |
| dc.date.available | 2012-01-18T10:28:28Z | |
| dc.date.issued | 2012-01-18 | |
| dc.description | MSc., Faculty of Science, University of the Witwatersrand, 2011 | en_US |
| dc.description.abstract | A study was performed in order to investigate the effect of preparation method and the effect of microwave heating on a manganese promoted iron based Fischer-Tropsch catalyst. The effects of preparation method and microwave heating on the structure and morphology of the catalyst, its surface area and reduction behavior were investigated using various techniques such as Transmission electron microscopy (TEM), Powder x-ray diffraction (PXRD), surface area measurements (BET) and temperature programmed reduction (TPR). The FTS performance of the catalysts were also studied using a fixed bed reactor with Fischer-Tropsch Synthesis conditions (270 C, flow rate of 30 ml/min, H2/CO ratio = 2, pressure of 10 bar). Characterization of the catalysts calcined at 350 C revealed that manganese enriched the surface of impregnated Mn/Fe catalysts and suppressed the reduction of the iron catalyst. However, the Mn acted as a structural promoter in the co-precipitated catalysts and also promoted the reduction of Fe2O3 as the manganese content increased. The co-precipitated catalyst calcined at 650 C suppressed the reduction of iron. The impregnated catalysts showed similar conversion (~ 70%) for catalysts with Mn loadings 5%, 10% and 20%. This suggests Mn promotes the activity of the iron catalyst since less iron is present in the catalyst as the manganese loading is increased. The co-precipitated catalysts showed a 10 wt% Mn loading to be the optimum amount for increased activity and selectivity to C2 – C4 hydrocarbons, lower molecular weight olefins and a lower selectivity to heavier molecular weight hydrocarbons relative to Mn loadings of 5, 20 and 50 wt%. Mn loadings in excess of 10 wt% showed a slight increase in selectivity to heavier weight hydrocarbons. The impregnated catalysts showed very little difference in activity and selectivity but the co-precipitated catalyst showed a decrease in activity after the catalyst was microwave heated. A slight increase in selectivity to lower weight olefins and heavier molecular weight hydrocarbons was noted after microwave heating. The TPSR (Temperature programmed surface reaction) results revealed that this may be due to the stronger adsorption of CO on the surface of the catalyst after microwave heating. A similar trend was observed for catalysts promoted with 0.1 wt% potassium i.e. a slight increase in selectivity to heavier weight hydrocarbons after microwave heating. | en_US |
| dc.identifier.uri | http://hdl.handle.net/10539/11077 | |
| dc.language.iso | en | en_US |
| dc.subject | Fischer-Tropsch process | en_US |
| dc.subject | Catalysis | en_US |
| dc.subject | Synthesis | en_US |
| dc.subject | Catalysts | en_US |
| dc.subject | Solid state chemistry | en_US |
| dc.title | The effect of microwave heating on manganese promoted iron based Fischer-Tropsch catalysts | en_US |
| dc.type | Thesis | en_US |