No abstract

The characterization of heavy petroleum fractions is essential for the design and improvement of cracking plants converting heavy feedstock into valuable "white" products. Conventional simulated distillation methods using packed columns are unsuitablefor this purposes, being limited to boiling points up to about 600OC. The method presented is able to cover a boiling points interval ranging from about 150°C up to around 800OC. It employs a short, nonpolar, highly thermostable capillary column routinely operated at temperatures around 430OC. The analytical system is based on a high temperatureversionof a fullyautoma-Dedicated to Professor Kurt Grob on his 65th birthday. tic, capillary dedicated gas chromatograph. The experimental data demonstrate that cold on-column injection is the sole sampling system suitable for such heavy compounds. The conversionof theretentiontimesinto boilingpoints, basedontheuseof low molecular weight polyethylenes, is extremely reliable, as demonstrated by the excellent retention time reproducibilities. The lower part (up to 550-600°C TBP) of the boiling point distribution curves of heavy petroleum fractionsobtained on capillary columns fits well with the corresponding distribution curves based on packed column data. For the petroleum fractionsfully eluted from the column the quantitative results obtained either using internal standards or by direct processing of the elution curves are in excellent agreement (less than 0.3 weight YO differences). The method has been applied to the determination of the true boiling points corresponding to short path vacuum distillation (DISTACT) cut points over 300OC. 0

We have always been impressed by No1 Venema's deep knowledge on the most various fields of analytical and organic chemistry. He was an extraordinary, creative scientist, left his trace in everything he did, was interesting to talk to and fascinating to listen to.He had shown interest, maybe even enthusiasm, for large volume on-column injection and we will not forget his contribution at Riva del Garda in September 94, given in his typical style, with modesty but always charming, clear, presenting findings based on hard experimental data.Abstract. Improved instrumentation facilitates on-column injection of up to several hundreds of microliters onto GC capillary columns. It incorporates an autosampler with adjustable injection speed, a standardized precolumn system, an early vapor exit, and software that models evaporation of a given solvent at the flow and temperature conditions chosen by the user. The software calculates the appropriate injection speed, guides the autosampler correspondingly, and closes the vapor exit at a moment leaving in the prccolumn the amount of unevaporated solvent that is selected by the user. o 199s John wilcy KC S o n s , Inc.