Synthesis of green fuels from biogenic waste through thermochemical route – The role of heterogeneous catalyst: A review

Using gas-to-liquids (GTL) technology will expand a new horizon as resources of crude oil diminish. Fischer–Tropsch synthesis (FTS) is a part of thermo-chemical route, which is used to produce chemicals, gasoline and diesel range fuel from synthesis gas derived from different sources, including coal, oil shale, tar sands, heavy residues, biomass, or natural gases. The FTS products are predominantly linear, since purified synthesis gases are used converting into sulfur and nitrogen free products. In this review the usage of bifunctional catalysts, where major contribution of promoters likes Rh-, Ru- with different modifiers like Zr, Ga, Si, Al, B, Cr, Ce, etc. and different supports like zeolites (ZSM-5), silica and alumina have been discussed. Selective synthesis of gasoline to higher-range hydrocarbons (C5+–C18+) and more have been discussed in different schematic ways, by considering different heterogeneous catalyst preparation techniques using various process parameters like mole H2/CO, CO2/(CO+CO2) ratios, pressures, temperatures, gas hourly space velocity and their effect on the CO% conversion. Catalytic activity and product selectivity studies with various methods of catalyst preparation technique and the characterization of different catalysts has also been discussed through this work. Different methods to modify the product distribution through thermo-chemical route by combining reaction engineering and improved catalysis synthesis techniques have been covered in this review.This may be realized through the development of new engineered catalysts tuned with careful control of mass transport effects. With new catalysts and optimal control of reactor operating conditions, the distribution of products could be tailored and/or maximized to meet market demands and thus maximize GTL plant operations.