Abstract: The invention provides a nickel upon transition alumina catalyst containing 5-40% ww of nickel, with an active nickel surface area between 80 and 300 m.sup.2 /g of Ni, with a transition alumina that satisfies the following X-ray diffraction pattern:______________________________________ d (10.sup.-10 m) I/Io ______________________________________ 1.39 100 2.85 75-85 2.72 60-80 2.43 70 2.01 45-80 ______________________________________Preferably, the BET total surface area of the catalyst is between 50 and 200 m.sup.2 /g catalyst and is substantially free from pores with a radius below 2.0 nm.Also, a process is provided for hydrotreating unsaturated hydrocarbons, in which unsaturated hydrocarbons are treated with hydrogen in the presence of a catalyst as defined above.

Abstract: The invention provides catalysts suitable for hydrotreatment of mineral oil which contain an oxide and/or sulphide derived from a metal of Group VI (B) and one from Group VIII metal and a transition alumina and which show an oxygen chemisorption above 185 micromoles per gram, preferably between 200 and 300. Preferably tha catalysts are free from anions of strong mineral acids.These catalysts can be prepared by impregnation of a transition alumina with an ammoniacal metal solution having an initial pH between 10.5 and 13, preferably between 11.0 and 12.5.