Original Paper Barman 311 J. Sep. Sci. 2004, 27, 311 – 315 www.jss-journal.de i 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Bhajendra N. Barman Shell Global Solutions (US) Inc., Westhollow Technology Center, P.O. Box 4327, Houston, TX 77251-4327, USA Hydrocarbon type analysis by thin-layer chromatography with flame-ionization detection: vacuum gas oils, heavy feeds, and hydroprocessed products Thin-layer chromatography with flame-ionization detection (TLC-FID) provides quan- titative hydrocarbon type data as well as distribution of aromatics by ring number. This method has been applied to obtain amounts of saturates, aromatics, and polars in heavy oil distillates such as light vacuum gas oils and heavy vacuum gas oils deriv- ed from different crude sources. TLC-FID chromatograms and resultant quantitative hydrocarbon type data show that these distillates vary markedly in aromatic contents and aromatic ring types. Similar observations are made with several fluid catalytic cracking feeds. Effects of process parameters such as operating pressure and tem- perature on hydroconversion of aromatics and polars from a heavy oil are assessed by TLC-FID. It has been demonstrated that there is a preferential reduction of higher polycyclic aromatic hydrocarbons and polars with an increase of both hydrogen partial pressure and reactor temperature. Key Words: Hydrocarbon type; Gas oils; Thin-layer chromatography; Flame-ionization detection; Hydroprocessing; Received: October 7, 2002; revised: March 18, 2003; accepted: January 23, 2004 DOI 10.1002/jssc.200201479 1 Introduction Heavy distillates such as vacuum gas oils and fluid cataly- tic cracking (FCC) feeds are very complex, containing hundreds of individual hydrocarbons varying in size and molecular structure, polarity, and functional groups. Almost all heavy distillates contain polar materials, a majority of them being sulfur, nitrogen, and oxygen com- pounds. Since chemical groups determine the chemical properties, quality, or processability of heavy distillates, the hydrocarbon type analysis has been a preferred choice for the characterization of these samples [1]. Thin-layer chromatography with flame-ionization detec- tion (TLC-FID) has been applied for the determination of hydrocarbon types in various high boiling materials with initial boiling points at or above 2608C. These samples include lubricant base oils [2 – 4], oxidized products from the thermooxidation of base oils [4], high boiling residua or fractions derived from crude oils [3,5 – 8], and coal tar pitches [8 – 10]. In this work, the TLC-FID technique has been applied to reveal differences in light vacuum gas oils (LVGOs) and heavy vacuum gas oils (HVGOs) derived from different crude sources. TLC-FID chromatograms and resultant quantitative hydrocarbon type data for saturates, aro- matics, and polars indicate that these distillates vary markedly in aromatic contents and aromatic ring types. FCC feeds are also studied to assess differences in both hydrocarbon group contents and aromatic types. Finally, TLC-FID is shown to be a useful technique to determine the effects of process variables such as temperature and pressure in the hydroprocessing of heavy oil by tracking compositional changes in the hydrocarbon types, and specifically, the total aromatics and aromatic ring types. 2 Experimental 2.1 Samples Topped-off crude oil (atmospheric residuum) was fraction- ated by vacuum distillation to obtain LVGO and HVGO. All LVGO and HVGO samples were actual refinery streams obtained as 345 – 4558C and 455–5658C cuts, respec- tively. Four FCC feeds were also refinery streams. Hydro- treated products from a heavy gas oil were obtained from a pilot plant study using a commercial heavy oil catalyst under differing operational severities. An aromatic extract, commonly known as rubber extender oil, was also ana- lyzed. 2.2 TLC-FID method The details of the TLC-FID procedure were provided else- where [2]. It was shown that TLC-FID is capable of resolv- Correspondence: Bhajendra N. Barman, Shell Global Solutions (US) Inc., Westhollow Technology Center, P.O. Box 4327, Hous- ton, TX 77251-4327, USA. Phone: +1 281 544 6205. Fax: +1 281 544 7025. E-mail: bhajendra.barman@shell.com.