Designing, Assembling, Characterization, and Modeling Microchannel based Fischer Tropsch Synthesis (FTS) Reactor

Abstract

The relevance of Fischer-Tropsch synthesis is becoming increasingly relevant due to hydrocarbon emissions and the need for alternative fuel sources. This thesis investigates three unique studies two experimental studies which utilized a serpentine microchannel reactor with a cobalt catalyst on an alumina substrate and a computational study of the FTS reaction network. The experiments were analyzed using gas chromatographs with a helium ionization detector and a flame ionization detector. The initial experimental study investigated three distinct temperatures and three residence times and statistically analyzed the results, at 95% confidence, with the goal of determining their effect on carbon monoxide conversion, methane selectivity, C2-C4 selectivity and C5+ selectivity. The experiments fit the Anderson-Schulz-Flory distribution and showed good agreement with literature. The statistical model showed that temperature independently had a strong effect on CO conversion, methane selectivity, C2 to C4 selectivity and C5+ selectivity while residence time had an effect on all parameters except C5+ selectivity. The binary interaction had a effect only on the methane selectivity. The second experimental study explored three distinct temperatures and three H2/CO inlet ratios and were statistically analyzed, at 95% confidence, with the goal of determining their effect on carbon monoxide conversion, methane selectivity, C2-C4 selectivity and C5+ selectivity. The experiments fit the Anderson-Schulz-Flory distribution and showed good agreement with literature. The statistical model showed that temperature and H2/CO ratio independently had a strong effect on CO conversion, methane selectivity and C5+ selectivity while the binary interaction had an effect on the C2 to C4 selectivity. The final study involved completing an analysis of the carbide mechanism of Fischer-Tropschz synthesis, specifically pertaining to the elementary reaction steps. All elementary reactions were identified and written as chemical rate equations. These equation were subsequently simplified through use of literature from Density Functional Theory. The simplified reaction network and unsimplified (full) reaction network were put into MATLAB and solved using ODE15s. The systems showed good general agreement with differences occuring for longer hydrocarbon synthesis. The system was validated by reducing the rate constants found in the full reaction network but removed from the simplified network to zero. When this reduction was done, the two models showed full agreement.