Utilization of greenhouse gas carbon dioxide for cleaner Fischer-Tropsch diesel production

Fischer-Tropsch is one of the commercially available processes for producing clean synthetic fuel from syngas. Industrially, coal/petcoke/biomass to synthetic fuel processes emits a large amount of greenhouse gas carbon dioxide which itself be utilized to enhance fuel production. This work is an attempt to utilize waste carbon dioxide generated either by syngas clean-up or during Fischer-Tropsch reaction as a carbon source for liquid fuel generation. In particular, this research provides an insight into the atomic scale in-situ carbon dioxide formation pathways in Fischer-Tropsch reaction over monometallic iron, cobalt and bimetallic iron-cobalt catalysts supported over hierarchical HZSM-5. Density-Functional-Theory calculations were used to get the energy barriers of the carbon-dioxide formation reactions and the results were validated by experiments. The active surfaces used in the theoretical calculations were corroborated using X-ray diffraction, X-ray photoelectron, and Raman spectroscopic characterizations. The acidity of the catalysts which is an important characteristic for maximizing the yield of diesel product, was determined by Electrophilic Fukui functions and electrostatic surface potential maxima is found in good agreement with the acidity trends obtained using Pyridine-Fourier Transform Infrared spectroscopy and ammonia-Temperature Programmed Desorption. The inter-conversion of the oxide and the carbide phases of active metals during the reaction proves to be an essential step in the carbon dioxide Fischer-Tropsch reaction which reduces production cost while carbon dioxide utilization makes it an environmental friendly sustainable process.