Abstract: Catalyst comprising at least one zirconium oxide, characterized in that it consists, for at least 85% of its weight, of a thermally stable support with a specific surface greater than or equal to 150 m.sup.2 /g containing from 60 to 99 weight % of at least one zirconium oxide and from 40 to 1 weight % of at least one metal oxide of at least one metal chosen from the group consisting of metals from Groups V, VI and VII, noble metals such as ruthenium, osmium, rhodium, iridium and uranium, and the elements phosphorus, arsenic and sulphur, the support being obtained by the molten salts technique by introduction of a mixture of salts into a eutectic mixture of alkali metal nitrates or sulphates which, after dehydration, is maintained between 250.degree. and 550.degree. C., from 30 minutes to 5 hours.

Abstract: The invention involves the liquid phase hydroconversion of hydrocarbon charges containing heavy fractions, and more particularly their deep conversion, in which the charge is contacted with a dispersed catalyst in the presence of a polyaromatic additive. The catalyst is a sulfide of a hydrogenating metal (such as molybdenum, nickel or cobalt) generated in situ from a precursor. The additive has at least three aromatic cycles, has a boiling point exceeding 300.degree. C., and is added at a rate of 5 to 60% by weight based on the charge. Synergism between the catalyst and the additive makes it possible to reduce the catalyst quantity and/or improve the conversion and quality of the products.

Abstract: In a process for the production of methyl mercaptan by heating a gas comprising carbon monoxide and/or carbon dioxide, hydrogen sulphide and hydrogen in contact with a catalyst based upon a heavy metal sulphide, with recycling of the gas fraction which has not reacted, the gas to be recycled has removed from it water which it contains following the reaction in contact with the catalyst.