Thesis (M.Eng)--Chulalongkorn University, 1995

Catalytic hydrotreatment of used lubricating oil on different types of catalysts was investigated using used lubricating oil taken from automobile engine. The catalysts were CoMo/Al2O3, NiMo/Al2O3 and NiW/Al2O3. The catalytic hydrotreatment was performed in fixed-bed reactor at a pressure of 5.51 MPa, temperatures of 320,350 and 380℃ and liquid hourly space velocities (LHSV) of 0.5, 1.0 and 1.5 hr-1. Most of contaminants and additives in used lubricating oil were removed by solvent extraction before hydrotreating. The results showed that after hydrotreating, ASTM color, sulfur content, viscosity and acidity of product oils decreased while viscosity index and flash point were not clearly observed. The operating conditions of catalytic hydrotreatment affected properties of the product oils. ASTM color, sulfur content, viscosity, flash point and acidity decreased while viscosity index increased with increasing temperatures or decreasing LHSV. CoMo/Al2O3 catalyst produced the product oils which had the best ASTM color, acidity and viscosity index. NiMo/Al2O3 catalyst produced the product oils which had the lowest sulfur content while NiW/Al2O3 catalyst produced the product oils which had the best viscosity and flash point. Comparison of product oils properties with base lube oil specification showed that quality of the product oils was comparable with base lube oil at suitable operating condition. Suitable catalyst was CoMo/Al2O3 and suitable operating conditions for this catalyst were a temperature of 350℃, a pressure of 5.51 MPa and a liquid space velocity of 0.5 hr-1.