Catalyticdewaxing

Session: Hydrocarbons and Other Fossil Fuels C H E M C O N 0 5 , N e w D e l h i Catalytic Dewaxing Of Vacuum Distillates For Lube Base Stock Uttam Ray Chaudhuri, Shubhajit Dutta, Ritusree Paul, Pragati Giri, Debashish Mukerjee and Biplab Guchait Dept. of Chemical Technology, University of Calcutta, 92 A.P.C Road, Kolkata 700009 Email:[email protected] Keywords: pour point,viscosity i ndex,hydroisome risation ABSTRACT Hydrotreated lube distillate from refinery was dewaxed catalytically in a batch reactor with a zeolite catalyst in presence of hydrogen in the laboratory. Temperature and pressure during study were kept at around 250-300 o c and pressure 80-150 kg/cm 2 . A good reduction in pour point has been observed with minor change in the viscosity and viscosity index of the oil. INTRODUCTION Lube oil base stocks (LOBS) are obtained from vacuum distillation unit of refinery. Traditional method employs a solvent extraction unit to dearomatise the distillate oil selectively to adjust the viscosity index of oil followed by dewaxing to adjust pour point and finally hydrotreated to finished lube base stock. The finished LOBS has to satisfy desirable viscosity, viscosity index and pour point in addition to other properties. High viscosity is contributed by the aromatic and naphthenic hydrocarbons in the oil with low viscosity index. Whereas paraffinic hydrocarbons have high viscosity index but with low viscosity. Therfore, viscosity and viscosity index are determined by the relative proportions of the aromatic, naphthenic and paraffinic hydrocarbons in the oil. Presence of paraffinic hydrocarbon s in the oil is also responsible for formation o f solid wax amount of which varies with their proportion. However, aromatic and naphthenic hydrocarbons of high molecular weight also give rise to the same problem of solidification but at very low temperature. For the finished lube it is desirable that solidification point ( or pour point) should be as low as possible to avoid congealing of the lube oil in use. It is also observed that iso-paraffinic hydrocarbons (branched chain) are less prone to solidification as compared to normal or straight chain paraffins in the oil. Solvent treatment method involves use of solvents like furfural, methyle pyrrolodine, phenol, propane, methyl-ethyl ke tone etc for selective extraction of aromatic a nd paraffin. Thus, a good amount of aromatic and paraffinic oil are extracted out as a non- lube bye-products an d as a result of which the y ield of lube base stoc k is reduced. This extraction process is a two stage process where aromatic extraction is done in the first unit followed by removal of paraffinic hydrocarbons in the dewaxing unit. Both the steps involve solvent recovery units. Dewaxing process involves propane or ammonia refrigeration system with trains of precoolers and chillers. 1

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Catalyticdewaxing