Hydrogen-treating of Light Lubricating Oil Fractions

Abstract

Light lubricating oil fractions from Persian Gulf crude, treated with and without furfral solvent, dewaxed with benzol/ketone and further redistilled, were hydrogen-treated in the presence of a CoMo (sulfide)/Al₂O₃ catalyst. The hydrogen-treated oils were compared with spindle oils which were treated with sulfuric acid and clay. A bench-scale pilot plant containing 100cc of the catalyst was used for the hydrogen-treatment.
When the non-furfural treated feed stock was hydrogen-treated, the product oils of less Saybolt chromometer numbers and of a little higher nitrogen contents were obtained compared with an acid and clay-treated spindle oil from the same feed stock. However, under certain conditions, other characteristics of the hydrogen-treated oils were almost the same as those of the acid and clay-treated oil. As regards the hydrogen-treatment of the furfural-treated feed stock, the a product oils had less Saybolt chromometer numbers and of a little higher nitrogen contents, but in some cases, they showed better oxidation stability and thermal stability compared with acid and clay-treated premium grade spindle oil from the same feed stock. In both cases mentioned above, using furfural-treated and non-furfural-treated feed stock, viscosity of hydrogen-treated oils became a little lower than those of the feed stocks. This effect of viscosity reduction by hydrogen-treatment was due to hydrodesulfurization reactions which occurred even at relatively lower treating temperatures, and the same effect was further accelerated by hydrodecyclization and cracking reactions at relatively higher treating temperatures. The higher hydrogen partial pressures in the hydrogen-treatment gave the product spindle oils of higher Saybolt chromometer numbers.