High molecular weight waxes from Short Path Distillates of vacuum residue

Short Path Distillates of vacuum residue (boiling above 545 °C) is taken as feedstock for this study. Wax from this fraction is separated by solvent extraction method using methyl iso-butyl ketone (MIBK) as solvent. Both wax and the feedstock are characterised with the help of ASTM and IP procedures. Separated wax is fractionated at different temperatures, say 0–30 °C using MIBK as solvent. High temperature gas chromatography (HTGC) technique is used to study the distribution of alkane carbon number in all the fractions. It is observed that the wax contains very high molecular weight hydrocarbons as high as C₆₇H₁₃₆. HTGC technique as well as the Differential Scanning Calorimetry (DSC) indicates that all the fractions of the wax contain two types of hydrocarbons, one having high molecular weight alkanes (> 600) and another having low mol. wt. alkanes (~ 400). Thermal analysis by DSC technique further indicates that the wax is microcrystalline in nature having a low degree of crystallinity, 17%, as evidenced by XRD studies. Both high and low molecular weight waxes can also be separated based on their solubility characteristics.