ONLINE GAS-CHROMATOGRAPHIC ANALYSIS OF FISCHER-TROPSCH SYNTHESIS PRODUCTS FORMED IN A SUPERCRITICAL REACTION MEDIUM

C-1-C-30 products from Fischer-Tropsch synthesis, conducted in a super critical n-hexane medium over an Fe catalyst in a fixed-bed reactor, a re analyzed using on-line gas chromatography. A Hewlett-Packard 5890 S eries II gas chromatograph (GC) is modified to minimize the effects of condensation of the on-line sample in the transfer lines. The GC is c onfigured with a Supelco Petrocol DH capillary column connected to a f lame ionization detector (FID) and two 1.83 m x 3.18 mm stainless stee l columns placed in series, packed with. 80/100 mesh HayeSep D, connec ted to a thermal conductivity detector(TCD). It is shown that pressure and temperature affect the elution order of oxygenates relative to hy drocarbons in the nonpolar capillary column. This phenomenon is exploi ted for obtaining improved resolution; several distinct methods produc e similar elution orders. Ar, added to the syngas feed, is used to cal culate syngas conversion. All compounds eluting before hexane (C-1-C-5 , Other than 2-methylpropene/1-butene and propanal/propanone) and near ly all the major peaks eluting after hexane are resolved in the capill ary column. H-2, Ar, CO, CH4, CO2, and H2O are resolved in the packed columns. The method provides excellent quantitative measurement of com ponent mole fractions that are within the range of calibration.