Use of Liquid-Washed Guard Bed for Catalyst Protection in Slurry Phase Fischer-Tropsch
Publication Date: 2003-Nov-25
The IP.com Prior Art Database
Use of Liquid-Washed Guard Bed for
Catalyst Protection in Slurry Phase Fischer-Tropsch
Fischer-Tropsch (F-T) liquid hydrocarbons can be produced from synthesis gas using slurry phase reactors, where small powder-sized catalyst particles are suspended in a liquid hydrocarbon medium – usually the F-T product itself. Synthesis gas bubbles up through the slurry, and the H2 and CO present diffuse to the catalyst surface where they react to form the F-T liquids. Lighter hydrocarbons exit the reactor with unreacted synthesis gas, while the heavier hydrocarbon products remain in the reactor and are withdrawn continuously. These hydrocarbons are separated from catalyst particles by a variety of means, usually by filtration.
Fresh synthesis gas may contain trace species, such as sulfur, that poison the catalyst in the
F-T reactor. Conventional clean-up processes, such as amine washing, are expensive and often cannot reduce the contaminant level to that required for long catalyst life (typically < 1 part per million by volume (pppmv)). A guard bed system, which uses a fixed bed of pellets of the same catalytic material as the catalyst in the slurry reactor, would be expected to provide efficient deep removal of the containments. Fixed beds are good for this application as the contaminants usually are removed within the first few layers of the bed, and in general, capacity for removing the contaminants is high and well exceeds the level at which they would have poisoned the catalyst. This high capacity leads to long guard bed life and clean synthesis gas going on to the F-T process.
However, a problem may arise in such a guard bed due to reaction between the CO and H2 to make F-T hydrocarbons. While such a reaction is limited...