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Open Access Publications from the University of California

Development of a Fischer-Tropsch Gasoline Process for the Steam Hydrogasification Technology

  • Author(s): Li, Yang
  • Advisor(s): Norbeck, Joseph M
  • et al.

The CE-CERT Steam Hydrogasification Technology efficiently converts carbonaceous materials to high energetic synthesis gas. This thesis investigates the direct production of gasoline range liquid hydrocarbons with high iso-paraffin content from synthesis gas. The goal is to provide a process to efficiently produce renewable gasoline that can be used directly without modification of engine or infrastructure.

An H-ZSM-5 shell Co/Al2O3 Fischer-Tropsch catalyst is prepared using a secondary-growth hydrothermal synthesis method. The catalyst not only synthesizes long-chain hydrocarbons from synthesis gas, but also cracks and isomerizes them into gasoline-range hydrocarbons with high iso-paraffin content. Characterization results show that the catalyst has good H-ZSM-5 shell coverage with no cracks or pinholes, with a shell thickness is around 4.29 μm. H-ZSM-5 shell composition is confirmed by EDX and XRD. In addition, the zeolite-shell catalyst has a 10% increase of surface area, compared to a conventional Fischer-Tropsch catalyst.

A high-temperature high-pressure lab-scale continuous Fischer-Tropsch reactor with LabVIEW automation system was designed and built. The reactor system has online gas and liquid sampling capabilities. It also has a PID controller with gain scheduling for precise heating control during Fischer-Tropsch synthesis test. Safety during reactor operation is ensured with alarms and automatic emergency response system.

Performance of a H-ZSM-5 shell Co/Al2O3 Fischer-Tropsch catalyst was investigated under various conditions. A maximum CO conversion of 97.1%, with a highest gasoline yield of 58% and iso-paraffin selectivity of 14.3%, was obtained. Sensitivity analysis shows that reaction temperature significantly affects CO conversion and iso-paraffin selectivity. Catalyst silicon to aluminum ratio also influences iso-paraffin selectivity, but has no effect on CO conversion. In addition, H-ZSM-5 shell Co/Al2O3 Fischer-Tropsch catalyst has much less carbon deposition than conventional catalyst, which can help reduce catalyst deactivation rate.

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