TITLE:
Product Analysis of Supercritical Fischer-Tropsch Synthesis: Utilizing a Unique On-Line and Off-Line Gas Chromatographs Setup in a Bench-Scale Reactor Unit
AUTHORS:
Amro Kasht, Rehan Hussain, Minhaj Ghouri, Jan Blank, Nimir O. Elbashir
KEYWORDS:
Supercritical Fluids, Fischer-Trospch Synthesis, Gas Chromatography, Mass Spectrometry
JOURNAL NAME:
American Journal of Analytical Chemistry,
Vol.6 No.8,
July
16,
2015
ABSTRACT: The
utilization of supercritical fluids (SCF) in the Fischer-Tropsch Synthesis
(FTS) further complicates the hydrocarbon products identification and analysis
process due to the dilution of hydrocarbon peaks by the predominant solvent
peak. Therefore, in this project, a custom-made Gas Chromatography (GC)
analysis system was designed and implemented to identify and quantify SCF-FTS
products. The FTS products were identified using two different methods. The
first was through retention time matching by injecting standard solutions, and
the second was through the use of the GC/MS system. The quantification of CO
and CH4 was achieved by using external standards, where the CO
conversion was calculated by relating the peak area of CO to the peak area of
an internal standard (argon) while the CH4 selectivity was
calculated by relating the peak area of CH4 to that of CO. After
setting and calibrating the GC system, two reaction conditions (gas phase: 240°C, 20 bar syngas with 2:1 H2:CO
molar feed ratio and for the supercritical fluids FTS (SCF-FTS): 240°C, 65 bar with 20 bar syngas partial pressure
and 2:1 H2:CO molar feed ratio) were used to compare the different
FTS reaction media. The comparison between the gas phase FTS and the SCF-FTS
showed the following: carbon monoxide conversion was improved by 14% in the
SCF-FTS, while the hydrocarbon product profile SCF-FTS showed 78% reduction in
light hydrocarbons (C1 - C4) products, 35% increase in
middle distillates (C11 - C22) products compared to gas
phase FTS. These improvements have resulted in higher chain growth probability
for the SCF-FTS (α = 0.85) compared
to the gas phase FTS (α = 0.76).
These results are generally in agreement with previously reported enhancement
in the SCF-FTS[1].