Abstract: A process for producing lubricating oils of enhanced photostability by hydrogenating a lubricating oil fraction of a hydrocrackate in the presence of a palladium catalyst supported on a silica-containing refractory inorganic oxide carrier in which the silica content is less than 40 weight %.

Abstract: A catalyst and process are described for the conversion of heavy hydrocarbon oils comprising contacting the oil with hydrogen in the presence of a conversion catalyst containing a Group VI and/or VIII metal supported on a carrier preferably comprising silica and alumina, the catalyst having the following structural characteristics:1. the silica (SiO.sub.2) content is 0 to 30% by weight of the total amount of an alumina-containing carrier,2. the volume of the pores having a radius in the range from 0 to 300 A is greater than 0.30 ml/g,3. the volume of the pores having a radius in the range from 0 to 30 A is less than 25% of the volume of the pores having a radius in the range from 0 to 300 A,4. the volume of the pores having a radius in the range from 75 to 300 A is less than 40% of the volume of the pores having a radius in the range from 0 to 300 A,5. the volume of the pores having a radius in the range from 75 to 75,000 A is smaller than 0.25 ml/g.