Abstract: The present invention concerns binary zeolitic systems comprising two zeolites A and B having different crystalline structures while having common structural units. The crystals of the zeolite A form a central core surrounded by a crown of crystals of zeolite B, the zeolites A and B being disposed concentrically and following the same longitudinal axis. These systems are formed by the introduction of a nucleation gel containing germs of the zeolite A in a growth gel where the crystallization parameters are favorable to the crystallization of the zeolite B. The binary zeolitic systems are useful as catalysts for transforming hydrocarbons and more especially as cracking catalysts.

Abstract: This invention concerns an omega type zeolite of high thermal stability, present in the form of hexagonal prismatic monocrystals having scored or plane faces of 0.1 .mu.m in edge and 0.5 to 5 .mu.m in length, this zeolite being obtained through crystallization from a mother solution containing a silica source, alumina, metallic oxide, an organic cation and water, in which the alumina source is a crystalline aluminosilicate of which at least one part is in suspension in the mother solution. In its acid form this zeolite can be used as catalyst for hydration of olefins and isomeric change of xylenes.

Abstract: The present invention concerns binary zeolitic systems comprising two zeolites A and B having different crystalline structures while having common structural units. The crystals of the zeolite A form a central core surrounded by a crown of crystals of zeolite B, the zeolites A and B being disposed concentrically and following the same longitudinal axis. These systems are formed by the introduction of a nucleation gel containing seeds of the zeolite A in a growth gel where the crystallization parameters are favorable to the crystallization of the zeolite B. The binary zeolitic systems are useful as catalysts for transforming hydrocarbons and more especially as cracking catalysts.

Abstract: There are provided clays of laminated structure bridged by metallic oxides selected from oxides of aluminum and zirconium and containing from 10 to 50% and preferably from 20 to 40% of an oxide of the metal of the group of the lanthanides, preferably of cerium. The presence of cerium improves the thermal resistance during a dry calcination or even under humid air. The clays can be used as catalysts during the conversion of hydrocarbons.

Abstract: The invention concerns a process for upgrading olefinic gasolines containing C.sub.5 hydrocarbons, but free of C.sub.4 hydrocarbons, by etherification. It is characterized in that the tertiary olefins of the charge are reacted (1 and 2) with methanol; the reaction effluent being then extracted (3) with water, in order to separate an aqueous phase containing the major part of the unreacted methanol from a hydrocarbon phase containing the major part of the formed ethers. The aqueous phase is then introduced in a distillation zone (4) where water is separated from methanol and recycled to the extraction zone (3), whereas methanol is recycled to the etherification zone (1 and 2).

Abstract: A process for the preparation of aliphatic alcohols by hydration of olefins in the presence of a catalyst comprising a zeolitic crystalline silicoaluminate of the offretite type. The offretite used can be natural or sythetic. Particularly convenient among the olefins are olefins of low molecular weight having up to 5 carbon atoms. The alcohols obtained are used as solvents, as bases for lubricants and as adjuvants of essences.

Abstract: The invention relates to a process to improve the stability of a catalyst to be used for lowering the cloud or turbidity point and the filterability limit temperature of gas-oils.The catalyst is formed of a composite system constituting 5 to 90% of a hydrodesulfuration type catalyst A and 95 to 10% of a hydroconversion type catalyst B, these two catalysts being either mixed or superposed, in which case catalyst A forms the top of the catalytic bed.

Abstract: The invention relates to a process to improve the stability of a catalyst to be used for lowering the cloud or turbidity point and the filterability limit temperature of gas-oils.The catalyst is formed of a composite system constituting 5 to 90% of a hydrodesulfuration type catalyst A and 95 to 10% of a hydroconversion type catalyst B, these two catalysts being either mixed or superposed, in which case catalyst A forms the top of the catalytic bed.