Catalytic Cracking of Vacuum Gas Oil and Used Lubricating Oil on Oil Shale Ash

Abstract

In this research, Vacuum Gas Oil and/or used lubricating oil is subjected to thermal cracking (pyrolysis) after impregnation on oil shale ash to obtain lighter molecular weight components. The spent oil shale of the thermal cracking step is subjected to further heat treatment in open air at 950^oC to react any organic compounds and mineral carbon to metal oxide. Used and/or fresh lubricating oils are impregnated on oil shale ash particles. Ash is soaked for 24 hours to allow absorption of the VGO or lubricating oils into the pores of the ash material. Oil shale ash which is known to contain several metal oxides such as CaO, SiO₂, and lesser quantities of Fe₂O₃, Al₂O₃, K₂O, Na₂O, etc. possesses inherent catalytic nature to crack heavy hydrocarbons to produce lighter components.

The absorbed Vacuum Gas Oil and/or lubricating oil inside the pores of the oil shale ash, is allowed to crack at 600^oC temperature. Cracking of VGO is conducted in a fixed bed reactor under nitrogen, steam environments. The weight ratio of the absorbed oil into the pores to oil shale ash is 1:1 ratio.

The particle size was in the range of 20-25 mm. The liquid products indicated 20 vol% falls in the kerosene fraction specifications where as Approximately 50 vol% is diesel cut. Residue which boils at higher than 370 ^oC constituted about 30 vol% of the liquid distillate.

Steam presence in the reaction media affected the composition of the product as measured in density increase. The sulfur content of the produce is found to be 0.75 wt%.