Abstract
Fischer-Tropsch synthesis has been investigated over a commercial type cobalt-based catalyst (20 %Co/0.5 %Re/γ-Al2O3) by varying the H2/CO ratio (2.55–1.12), CO conversion (15–75 %), reaction temperature (210 °C, 230 °C), and by adding water to the syngas. The experiments were conducted in a fixed bed reactor with the main purpose of obtaining experimental data to be used in the development and fitting of a mechanistic model. A positive effect of water on the catalyst activity was found for experiments with a H2/CO ratio higher than 1.7. Water was found to always increase the C5+ selectivity regardless of the H2/CO ratio. Increasing conversion led to increased C5+ selectivity. The selectivity to CO2 was significantly enhanced at higher conversions (high water partial pressure), particularly with the lowest H2/CO = 1.12, interpreted as the emergence of water-gas shift activity. Re-oxidation of cobalt, probably limited to small cobalt particles, is proposed as the main deactivation mechanism caused by water while a steeper deactivation curve was found for higher temperature, indicating that sintering also may play a role.
Highlights
Fischer-Tropsch synthesis converts synthesis gas (H2 + CO) into a wide range of hydrocarbons that can be refined into drop-in commercial products like diesel and jet fuel [1]
Fischer-Tropsch synthesis has been investigated over a commercial type cobalt-based catalyst (20 %Co/0.5 %Re/ γ-Al2O3) by varying the H2/CO ratio (2.55–1.12), CO conversion (15–75 %), reaction temperature (210 ◦C, 230 ◦C), and by adding water to the syngas
The objective of this work is to investigate the effects of process conditions such as H2/CO ratio (2.5− 1.0), CO conversion level (15–75%), added water in the syngas, and temperature (230 ◦C, 210 ◦C) on activity and selectivity of a commercial type cobalt-based FischerTropsch catalyst
Summary
Fischer-Tropsch synthesis converts synthesis gas (H2 + CO) into a wide range of hydrocarbons that can be refined into drop-in commercial products like diesel and jet fuel [1]. Syngas may be derived from natural gas, coal, and biomass. The related processes are called GTL (gas-to-li quids), CTL (coal-to-liquids) or BTL (biomass-to-liquids) [2]. Liquid fuels produced via the Fischer-Tropsch process from biomass-derived syngas promises an attractive, clean, carbon-neutral and sustainable energy source [5]. The possibility to work with the existing fuel infrastructure and versatility in feedstock and products are key advantages of using the BTL-FTS process route. Another benefit is the ability to utilize the whole organic biomass matter. Biomass represents the only practical renewable source of carbon, necessary for the production of liquid hydrocarbon fuels and chemicals [6]
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