A Review of the Use of Carbon Nanostructures and Other Reducing Agents During Auto-reduction for Fischer–Tropsch Synthesis and Other Applications

Abstract

Fischer–Tropsch Synthesis (FTS) is an important process in the production of liquid fuels in the energy sector, due to its flexibility for use with other technologies that can produce carbon monoxide (CO) and hydrogen. Catalysts have found substantial use in FTS to improve the process efficiency. However, the use of conventional FTS catalyst reduction techniques using (hydrogen (H2), CO and syngas) to activate the metal precursor has been accompanied by strong metal-support interactions. Such limitations have driven the quest for better technologies to ensure FTS catalysis reaches its full capacity. In this article, we review the activation techniques used, with emphasis on the contemporary auto-reduction technique, which has revealed energy-saving merits. Auto-reduction has the advantage of reducing the number of steps involved in catalyst preparation prior to FTS as well as eliminating costly reducing agents such as H2, CO and syngas. Auto-reduction in this article refers to the reduction of the metal precursor using a carbon support. We firstly provide a comprehensive review of the traditional reducing agents, followed by a review of the contemporary auto-reduction technique. A comparison of the conventional FTS catalyst reduction and auto-reduction techniques is provided to allow for a fundamental understanding of the merits and demerits of both techniques. The different types of nanostructured carbon materials used in aiding auto-reduction for the FTS process are reviewed.Graphical