Scaling of the Technology for Producing C19+ Hydrocarbons in Fischer-Tropsch Synthesis: Transition from Laboratory Research to Pilot Testing

Abstract

This paper examines the scaling of a technology for the selective synthesis of high-molecular-weight C19+ hydrocarbons (synthetic waxes) from CO and H2 in the Fischer-Tropsch synthesis (FTS) process over a cobalt-aluminum-silica catalyst. Scaling was performed using a 6-meter tubular reactor at a pilot plant using natural gas as feedstock. During 557-hour tests, a C5+ productivity of 36.6 kg/(m³cat h) and a C19+ selectivity of 49-53% by weight were achieved. The stability of the catalyst was confirmed, and three characteristic periods of catalyst operation were identified: activation, stable operation, and deactivation caused by wax accumulation. A key effect of scale on the process hydrodynamics was established: increasing the reactor diameter and catalyst granule size shifts the synthesis regime from laminar (Re ~ 0.45 under laboratory conditions) to transient (Re = 10.9 under industrial conditions), which increases heat transfer but reduces C5+ selectivity from 82.1% to 69.6%, while maintaining a high proportion of C19+ in the products. Based on an analysis of the thermal and hydrodynamic characteristics, the need to maintain laminar conditions (Re < 10) in industrial reactors to maximize wax yield was substantiated. The results of pilot tests and the proposed engineering solutions demonstrate the viability of the technology for creating competitive industrial production in Russia.