Breakthrough in conversion of abundant natural resources such as natural gas, biomass, and coal to ultra-clean fuels and value added chemicals requires design of non-conventional and energy integrated technologies. This book provides fundamentals and applications for the utilization of non-conventional reaction media such as the supercritical fluids in the Fischer Tropsch reactor, which is the heart of gas-to-liquid technology. This medium provides unique properties between the gas and the liquid reaction media and yields a highly efficient reactor system that can provide several advantages over the current commercial technologies.