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 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.
van der Westhuizen
Rina
R
Sasol Technology R&D, Sasolburg 1947, South Africa.
Potgieter
Hein
H
Prinsloo
Nico
N
de Villiers
André
A
Sandra
Pat
P
D001966:Bromine / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D003516:Cycloparaffins / Q000032:analysis* / Q000302:isolation & purification; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D005742:Gasoline / Q000032:analysis; D007648:Kerosene / Q000032:analysis; D058105:Polymerization; D012834:Silver / Q000737:chemistry
D003516:Cycloparaffins; D005742:Gasoline; D007648:Kerosene; D012834:Silver; D001966:Bromine