Debunking the impact of crystallite/particle size in cobalt-based Fischer-Tropsch synthesis
Joshua Gorimbo, Roick Chikati, Phathutshedzo Khangale, Isaac N. Beas, Liberty L. Mguni, Diankanua Nkazi
Abstract
This review examines the relationship between the crystallite size of cobalt and the distribution of products produced by Fischer-Tropsch synthesis (FTS). The ideal range for the average cobalt crystallite diameter is between 6 and 8 nm. Deviating from this range, whether by increasing or decreasing the crystallite size, influences the carbon monoxide (CO) turnover frequency and the selectivity of CH4, C2-C4, and C5+. To ensure the development of a consistent catalyst, careful monitoring and adjustment of the morphology, particle size, and metal loading on the support particles are essential. For experimental repeatability during FTS applications, it would be ideal if catalyst particles had crystallites of a uniform size. Methods for crystallite characterization and catalyst synthesis were also addressed in detail. The diameter of the cobalt crystallite appears to be a crucial parameter that influences cobalt oxidation, the thermodynamics of cobalt reduction and oxidation are reported. Conducting a Design of Experiment (DOE) with Design Experts on available literature led to determining optimal conditions for enhancing the primary target product of FTS—C5+ selectivity.