Simulated distillation of petroleum residues by capillary SFC

A method for determining boiling points for heavy residues of petroleum by simulated distillation using a supercritical fluid chromatography apparatus, said supercritical fluid chromatography apparatus having a chromatographic column with an injection end and an exit end with a mobile phase located therebetween having a supercritical temperature, said column having at least a portion thereof located in a gas chromatographic oven, comprising the steps of:

• establishing a temperature T1 in said gas chromatographic oven, and maintaining that temperature, the temperature T1 being at or above the supercritical temperature of the mobile phase and in a range of 100 degrees C. to 180 degrees C.;
• establishing at the injection end of the column, a pressure program p(t) as a function of time t beginning at an initial pressure p1 and ending at a final pressure p2, the program to take place over an interval of time t1, the time t to begin when a sample is injected into the column;
• injecting a first sample into the column, said first sample being comprised of materials having known boiling points;
• eluting the first sample from the exit end of the column during the time interval t1;
• detecting the first sample eluted from the column using flame ionization detection techniques, to obtain a chromatogram of the first sample;
• correlating retention time of peaks in the chromatogram of the first sample with the known boiling points for the materials comprising the first sample, to obtain a calibration function relating elution time to boiling point;
• reinitiating the pressure program p(t) after the time interval t1, the pressure program to begin when a second sample is injected into the column;
• injecting the second sample into the column, said second sample having boiling point over 250 degrees C.;
• eluting the second sample from the column over a second interval of time equal to t1;
• detecting the second sample eluted during the second interval of time to obtain a chromatogram of the second sample having a set of retention times;
• and
• evaluating said calibration function at said retention times of said second sample to obtain a boiling point distribution for the second sample.