(569fd) Deactivation Mechanisms of Iron-Based Catalysts in Fischer-Tropsch Synthesis: Insights from Extended Time-on-Stream Studies and Multi-Technique Analysis

Iron catalysts are predominantly utilized in Fischer-Tropsch synthesis (FTS) owing to their economic viability and natural abundance. Despite extensive research, the mechanisms underlying catalyst deactivation, including sintering, oxidation, and carbon deposition, remain incompletely understood. This study investigates the deactivation modes of a commercial iron-based catalyst over prolonged time-on-stream (TOS), focusing on oxidation, sintering, and graphitization processes. Experimental analyses employing XRD, XPS, FTIR, HRTEM, and TGA techniques are conducted on industrial Fe/SiO2 catalyst samples retrieved from a fixed-bed reactor operating under realistic FTS conditions. The findings indicate that sintering may not be a primary deactivation mechanism over extended TOS durations. Moreover, a comprehensive review of pertinent literature is integrated to elucidate the sintering and oxidation behavior of metallic iron during FTS. Discrepancies in existing literature are attributed to the absence of direct measurements of iron clusters and variations in catalyst crystallite sizes and operating conditions such as reactor partial pressures of hydrogen and water. These fluctuations impede accurate prediction of sintering kinetics, underscoring the complexity of FTS catalyst deactivation mechanisms.