Abstract: The invention relates to a process for the conversion of petroleum hydrocarbons in the presence of catalyst particles in a fluidized phase in an essentially upflow or downflow tubular reaction zone. The process includes at least one stage of steam cracking of at least one light hydrocarbon fraction and a stage of catalytic cracking of at least one heavy hydrocarbon fraction. The steam cracking is carried out by contacting the light hydrocarbons and a quantity of steam equal to at least 20 percent by weight in a fluidized bed of the catalyst particles, the resulting temperature ranging from 650.degree. to 850.degree. C. The catalytic cracking of the heavy hydrocarbons is carried out by injection of the effluents from the upstream section of the reaction zone into the catalyst suspension in such a way that the temperature of the mixture ranges from 500.degree. to 650.degree. C. and is then reduced to a temperature ranging 475.degree. to 550.degree. C.

Abstract: The invention relates to a process for the conversion of petroleum hydrocarbons in the presence of catalyst particles in a fluidized phase in an essentially upflow or downflow tubular reaction zone, said process comprising at least one stage of steam cracking of at least one light hydrocarbon fraction and a stage of catalytic cracking of at least one heavy hydrocarbon fraction.The steam cracking is carried out by contacting the light hydrocarbons and a quantity of steam equal to at least 20 percent by weight in a fluidized bed of the catalyst particles, the resulting temperature ranging from 650.degree. to 850.degree. C.The catalytic cracking of the heavy hydrocarbons is carried out by contacting them with the effluents from the upstream section of the reaction zone and the catalyst suspension in such a way that the temperature of the mixture ranges from 500.degree. to 650.degree. C. and is then reduced to a temperature ranging from 475.degree. to 550.degree. C.

Abstract: Catalytic conversion of a hydrocarbon feedstock comprising a stage of catalytic cracking of a hydrocarbon feedstock, a stage of separation of the products of cracking from the catalytic mass, and a stage of regeneration and recycling of the catalytic mass and between the stage of regeneration of the catalytic mass and the stage of separation of the products of cracking there is injected continuously or intermittently, at one or more points, in admixture with at least one hydrocarbon to be treated, at least one diorganophosphite of the general formula ##STR1## where R.sub.1 and R.sub.2, which may be alike or different, are selected from the group consisting of alkyl, aryl or aralkyl groups having from 1 to 30 carbon atoms.