Fractionation by liquid chromatography combined with comprehensive two-dimensional gas chromatography–mass spectrometry for analysis of cyclics in oligomerisation products of Fischer–Tropsch derived light alkenes

In oligomerisation products of High Temperature Fischer–Tropsch (HTFT) derived light alkenes using a solid phosphoric acid (SPA) catalyst, the presence of cyclics was presumed although their occurrence could not be explained by the generally accepted oligomerisation mechanism. Notwithstanding the us...

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Bibliographic Details
Published in:Journal of Chromatography A 2011-05, Vol.1218 (21), p.3173-3179
Main Authors: van der Westhuizen, Rina, Potgieter, Hein, Prinsloo, Nico, de Villiers, André, Sandra, Pat
Format: Article
Language:English
Subjects:
alkanes
Alkenes
Analytical chemistry
Catalysts
Catalytic polymerisation
Chemistry
Chromatographic methods and physical methods associated with chromatography
Chromatography
Comprehensive GC
Deactivation
Exact sciences and technology
Fractionation
Gas chromatographic methods
gas chromatography-mass spectrometry
Liquid chromatography
molecular weight
Oligomerization
Other chromatographic methods
Phosphoric acid
Separation of cyclic alkanes and alkenes
Silver-ion modified column
Spectrometry
temperature
Two dimensional
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Summary:In oligomerisation products of High Temperature Fischer–Tropsch (HTFT) derived light alkenes using a solid phosphoric acid (SPA) catalyst, the presence of cyclics was presumed although their occurrence could not be explained by the generally accepted oligomerisation mechanism. Notwithstanding the use of GC×GC-TOFMS, the cyclic alkanes could not be differentiated from the alkenes. On the one hand, compounds co-eluted in GC×GC and, on the other hand, MS cannot distinguish between these classes because of identical molecular masses and very similar mass fragmentation patterns. An LC pre-fractionation procedure utilising a silver-modified column was developed to separate the saturates from the unsaturates. Using this approach we were able, for the first time, to confirm the presence of cyclics, probably resulting from secondary reactions, in HTFT oligomerisation products. The occurrence of cyclics can be an indication of the beginning of carbonaceous deposit formation that could eventually lead to catalyst deactivation.
ISSN:0021-9673
DOI:10.1016/j.chroma.2010.10.009