THE CHARACTERIZATION AND QUANTITATION OF SULFUR-CONTAINING-COMPOUNDS IN (HEAVY) MIDDLE DISTILLATES BY LC-GC-FID-SCD

A modified sulfur chemiluminescence detector (SCD) has been interfaced to a HPLC-HRGC hyphenated system, This combination enables the full c haracterization and quantitation of the sulfur containing compounds in (heavy) middle distillate oil fractions (boiling range 150-450 degree s C), The system is suited to identify and determine the various group s of organo-sulfur structures such as: thiols + sulfides + thiophenes, benzothiophenes, dibenzothiophenes and benzo-naphthothiophenes. Withi n these groups a separation according to boiling point is accomplished . Therefore it allows the separation, identification and quantitation of a number of individual species, especially those which are refracto ry to hydrodesulfurization (HDS), such as 3-methyl-benzothiophene, 4-m ethyl-dibenzothiophene and 4,6-dimethyl-dibenzothiophene. The analysis of these groups and specific compounds is the key in understanding th e kinetics of the chemistry involved in HDS, The complete instrumental set-up is fully automated by computer control, To suppress possible i nterferences and quenching of the sulfur response of the SCD from (lar ge amounts of) hydrocarbons, it is aligned above the adapted flame ion ization detector (FID) of the GC, This renders a sensitivity of the SC D for sulfur of 2 pg.s(-1), which corresponds to a minimum detectable level for individual sulfur species in oil fractions for the complete system of 1 ppm (mg.kg(-1)) sulfur. Its linear dynamic range exceeds 1 0(5), which means that also untreated, high sulfur containing feedstoc ks can be analyzed directly. The selectivity of sulfur to carbon of th e modified SCD exceeds 10(6). A number of HDS feedstocks and desulfuri zed products of different desulfurization levels have been analyzed wi th the system, From the analysis results the behavior of the refractor y compounds in HDS can now be followed closely.