Abstract: A modified or bridged asphalt composition. The composition can be obtained by treating at least one asphalt base with an acid-derived compound having at least two functional groups capable, respectively, of being grafted onto one or more sites located on two or more different aromatic entities of the asphalt base, so as to link said entities by bridging.

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: A process for the thermal conversion of various fossil organic materials such as heavy crude oils, heavy petroleum fractions or refining residues, is described. According to the invention, the charge is subjected to thermal processing in the presence of a minor proportion of at least one radical-generating monooxygenated compound, containing at least one heteroelement selected from sulfur, and nitrogen and in which the oxygen is borne by said heteroelement. The conversion is improved with a composition comprising a hydrogen donor diluent and this monooxygenated compound in a weight ratio of 0.2:1 to 400:1. The invention is useful in the petroleum industry and the coal industry and particularly in the process of hydrovisbreaking.