An extension of ASTM D7169 is shown using new Zebron ZB-1XT SimDist metal GC columns.
Kory Kelly, Chris Fernandez, and Ngoc Nguyen, Phenomenex, Inc.
An extension of ASTM D7169 is shown using new Zebron ZB-1XT SimDist metal GC columns. This method extends the analysis to C120 while easily surpassing method requirements including peak shape and efficiency.
When refining petroleum, it is necessary to determine the composition of raw materials as well as finished products to ensure that reactants are being processed effectively and that the highest possible efficiency is maintained. A sample's composition is determined by creating a boiling point distribution profile that correlates to the hydrocarbon distribution within that sample. Refineries continually try to extend the range of analysis to include wider boiling points because that gives more information about their materials and allows them to better plan processing.
Typically, crude oil and heavier range products contain a lot of high molecular weight compounds that require high boiling point simulated distillations. ASTM D7169 is such a method. It extends the range of the previous method ASTM D6352 from C90 to C100.
The method presented here extends that range even further by going to C120, while still surpassing the performance requirements of the current ASTM D7169 method.
A Zebron ZB-1 SimDist 5 m x 0.53 mm x 0.09 µm column was used with an oven program of 35 °C to 430 °C at 9 °C/min for 10 min. A 1.0 µL injection of hydrocarbon standards with POLYWAX 1000 in carbon disulfide was made on-column with FID detection at 450 °C. Helium carrier gas was used at 34.0 mL/min.
The ASTM method D7169 has system performance requirements for resolution, peak skew, and temperature program. Resolution between C50 and C52 must be between 1.8 and 4.0. The skew of any peak between C12 to C24 needs to be between 0.8 and 1.2. The last compound that can be included in the analysis needs to elute on the temperature program.
Using a Zebron ZB-1XT SimDist GC column, all method requirements were met. The minimum resolution requirement was surpassed with a value of 2.55. The average peak skew of all peaks from C12–C24 had near perfect symmetry of 0.99 and covered a narrow range from 0.94 to 1.06. The last peak that elutes on the temperature program has been extended to include the very high boiling C120 (Figure 1).
Figure 1: ASTM D7169 standard using a Zebron ZB-1XT SimDist column of 5 m x 0.53 mm x 0.09 Âµm dimensions with elution of C120 on the temperature ramp.
The new Zebron ZB-1XT SimDist metal columns show excellent performance for high temperature simulated distillation methods like ASTM D7169. The requirements of the method were easily met while still allowing for an extended range of hydrocarbons up to C120 program without going above 430 °C. The ease of meeting system requirements means less downtime for maintenance. The extended range of compounds from this analysis gives a refinery a greater understanding of its samples. This knowledge can aid in process planning and increase product yields which directly affect the bottom line.
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