Abstract: A process for the production of paraxylene is described that comprises an adsorption stage (18) that uses toluene as a desorbent in a simulated moving bed of a feedstock whose ethylbenzene was separated by distillation (line 3) or by adsorption, an isomerization stage (26) without hydrogen in liquid phase that is diluted with toluene from the raffinate produced, a distillation stage (27) of the raffinate that is isomerized to recover the toluene (line 29) that is recycled. The separated isomerate is introduced into a xylene distillation column (9) then recycled, in adsorption. The separated ethylbenzene is isomerized separately in gas phase with hydrogen at higher temperature and is distilled (5, 2, 9) in the presence of a catalyst that comprises an EUO-structural-type zeolite, then recycled in adsorption column (18). The pure paraxylene is collected as extract (line 22) then optionally purified by crystallization (17).

Abstract: A process for the production of at least one isomer of xylenes comprising a simulated moving-bed adsorption (8) of a C8-aromatic feedstock (1) that delivers a paraxylene-rich fraction (9) that is optionally purified after a distillation (16) by at least one high-temperature crystallization (5) and a fraction (10) that is low in paraxylene is described. Fraction (10) is distilled and then isomerized (21) in the presence of an EUO-structural-type catalyst. The lightest hydrocarbons are removed from the isomerization effluent in a first distillation (23) then naphthenes in a second distillation (26), and distilled isomerization effluent (2) that results therefrom is recycled at least in part in adsorption (8). A mother liquor (3) that results from the crystallization stage is recycled at least in part in adsorption (8).

Abstract: A process for co-production of paraxylene and ethylbenzene comprises: (A) an adsorption stage of a feedstock of xylenes and ethylbenzene in a simulated moving bed that produces an extract of pure paraxylene and an ethylbenzene-rich raffinate; (B) an adsorption stage in a simulated moving bed, of raffinate from which desorbent has been removed that supplies an essentially pure ethylbenzene extract and an orthoxylene and metaxylene raffinate that contains desorbent; (C) a recover stage for the desorbent; (D) an isomerization stage for the orthoxylene and metaxylene raffinate in the presence of a catalyst that comprises an EUO-type zeolite; and (E) a stage for recycling the isomerate that is produced with adsorption.

Abstract: Process for isomerization of a feedstock that contains aromatic compounds with eight carbon atoms characterized in that it comprises at least one isomerization stage a) that is carried out in the presence of a catalyst that contains at least one metal of group VIII and that is activated according to an activation process that comprises at least one sulfurization stage and at least one stage for passivation with ammonia, and at least one dehydrogenation stage b).

Abstract: The present invention concerns a process for preparing a zeolite with structure type EUO comprising at least one element X selected from silicon and germanium and at least one element T selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, characterized in that seeds of at least one zeolitic material are used comprising at least one element X′ selected from silicon and germanium and at least one element T′ selected from iron, aluminium, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese with a ratio X′/T′ of less than 200, said seeds being different from the zeolite with structure type EUO being prepared.

Abstract: A process for isomerising aromatic compounds containing eight carbon atoms is described in which the catalyst used contains at least one zeolite with structure type EUO and a group VIII element. In FIG. 1, the feed to be isomerised is introduced into reactor R via line 1. This fresh feed is enriched via lines 6 and 11 with a mixture containing at least one compound selected from the group formed by paraffins containing eight carbon atoms, benzene, toluene and naphthenes containing eight carbon atoms. Hydrogen is added via line 15.

Abstract: A process for synthesising a zeolite with structure type EUO comprising at least one element X selected from silicon and germanium and at least one element T selected from aluminum, iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, antimony, chromium and manganese, comprises reacting an aqueous mixture comprising at least one source of at least one element X, at least one source of at least one element T, and at least one precursor of an organic compound comprising at least one alkylated polymethylene &agr;-&ohgr; diammonium derivative, wherein at least one precursor is selected from monoamines. The zeolite obtained is used as a catalyst in a process for converting hydrocarbon-containing feeds, as an adsorbent to control pollution and as a molecular sieve for separation, and particularly for isomerising aromatic compounds containing 8 carbon atoms.

Abstract: The present invention relates to a process for activating catalysts for isomerizing aromatic compounds containing 8 carbon atoms, the catalysts containing at least one group VIII metal, comprising at least one sulfurization and at least one passivation using ammonia.

Abstract: Process for isomerization of a feedstock that contains aromatic compounds with eight carbon atoms characterized in that it comprises at least one isomerization stage a) that is carried out in the presence of a catalyst that contains at least one metal of group VIII and that is activated according to an activation process that comprises at least one sulfurization stage and at least one stage for passivation with ammonia, and at least one dehydrogenation stage b).

Abstract: The present invention relates to a process for isomerizing aromatic compounds containing 8 carbon atoms, the catalysts containing at least one group VIII metal, comprising at least one sulfurization step and at least one passivation step using ammonia.

Abstract: A process for isomerising a feed comprising aromatic compounds containing 8 carbon atoms is carried out in two steps: an isomerisation step and a dehydrogenation step. In FIG. 1, the feed to be treated is introduced into isomerisation zone R1 via line 1. Substantially pure hydrogen is introduced into line 1 via line 12 and recycled hydrogen is introduced into line 1 via line 13. Hydrogen which circulates in line 13 is purged via line 15. The effluent from isomerisation zone R1 is sent to a separation zone S1 via line 2. In S1, hydrogen contained in the effluent is isolated and recycled to the inlet to isomerisation zone R1 via line 13, the remaining effluent being evacuated from this separation zone S1 via line 3. The fluid contained in line 3 is heated in an oven F1 then evacuated therefrom via line 4. The effluent leaving the oven is enriched in recycled hydrogen via line 14 then it is introduced into dehydrogenation zone R2. The effluent from zone R2 is sent via line 5 to separation zone S2.

Abstract: For isomerising aromatic compounds containing eight carbon atoms in the presence of hydrogen, a mixture containing compounds with a boiling point of about 80° C. to 135° C. comprising at least one paraffin containing eight carbon atoms, at least one naphthene containing eight carbon atoms, at least benzene and at least toluene is added to the feed before introducing it into the isomerisation reactor R via line 1. These additions are made by a recycle via line 6 or by adding fresh compounds via line 11, or be a combination of fresh and recycled compounds via lines 6 and 11. Hydrogen is added via line 15.

Abstract: A C.sub.8 aromatic feedstock is isomerized by an isomerization stage conducted at 320-380.degree. C. with a catalyst containing at least one EUO-structure-type zeolite and at least one metal of group VIII, to obtain an effluent containing isomerized alkyl aromatics and about 10-30% by weight of naphthenes. The effluent is then subjected to a dehydrogenation stage so as to convert the naphthenes to additional alkyl aromatics.

Abstract: A device for testing the development of processes or chemical reactions in the presence of solid catalysts comprising a reactor of cylindrical shape, of inside diameter D and of length L, such that 50<L/D<150. The reactor having a preferred D of 10-40 mm also includes a sheathed thermometer arranged substantially along the axis of the reactor.