Process for converting heavy hydrocarbon oils, containing asphaltenes, to lighter fractions

A process for converting an asphaltenic oil to lighter fractions, which comprises the steps of:

• (a) deasphalting the asphaltenic oil with an aliphatic C.sub.5-7 hydrocarbon solvent, said deasphalting being effected under conditions such that the major part of the resins remains in the deasphalted oil, and recovering the resultant deasphalted oil;
• (b) maintaining the deasphalted oil with hydrogen at 440.degree.-530.degree. C. for 1 second to 10 hours, under a pressure of 40 to 140 bars, in a non-catalytic conversion zone;
• (c) feeding the product of step (b) with hydrogen into a catalytic conversion zone at 320.degree.-430.degree. C., under a pressure of 40 to 140 bars, in contact with at least one catalyst comprising at least one molybdenum compound or tungsten compound or a mixture thereof and at least one nickel compound or cobalt compound or a mixture thereof, and recovering the resultant hydrocarbon fractions.