Investigation of Asphaltene Precipitation at Elevated Temperature

In order to obtain quantitative data on the asphaltene precipitation induced by the addition of n-alkane (heptane) at temperatures above the normal boiling point of the precipitant, a high temperature/high pressure filtration apparatus has been constructed. Oil and alkane are mixed at the appropriate temperature and the pressure in closed vessels keeping the mixture at the liquid state. The filtration is performed with a small differential pressure over the filter so as to avoid flashing the mixture. The technique requires a low dead volume in the system to minimize the content of maltenes in the extracted fraction, hence there is no room for stirring. The equipment as well as solutions to some of the problems are presented along with precipitation data from 40 to 200 degrees C. The asphaltenes separated are analyzed using FT-ir. The filtrate containing the maltenes was cooled to room temperature and the asphaltenes separating upon cooling was collected and analyzed. The oil and selected maltene fractions and extraction/cleaning solvents were analyzed using GC.