Abstract: To continuously produce and separate high purity p-xylene from a C.sub.8 aromatic hydrocarbon charge, successive use is made in combination of (1) a stage of separating low-purity p-xylene (75 to 98%) by simulated moving bed adsorption chromatography; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25 to +10.degree. C.); (3) a stage of catalytic isomerization of the charge which has been p-xylene-depleted by the separating stage (1); and recovering an isomerate which is then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: To continuously produce and separate high purity p-xylene from a C.sub.8 aromatic hydrocarbon charge, successive use is made in combination of (1) a stage of separating low-purity p-xylene (75 to 98%) by simulated moving bed adsorption chromatography, with a ratio for the solvent to charge flow rates of 1.2 to 2.5; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25.degree. to +10.degree. C.); (3) a stage of catalytic isomerization of the charge which has been p-xylene-depleted by the separating stage (1); and recovering an isomerate which is then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: To continuously produce and separate high purity p-xylene from a C.sub.8 aromatic hydrocarbon charge, successive use is made in combination of (1) a stage of separating low-purity p-xylene (75 to 98%) by simulated moving bed adsorption chromatography, with a ratio of the solvent to charge flow rates of 1.2 to 2.5; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25 to +10.degree. C.); (3) a stage of catalytic isomerization of the charge which has been p-xylene-depleted by the separating stage (1); and recovering an isomerate which is then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: To continuously produce and separate high purity p-xylene from a C.sub.8 aromatic hydrocarbon charge, successive use is made in combination of (1) a stage of separating low-purity p-xylene (75 to 98%) by simulated moving bed adsorption chromatography, with a ratio of the solvent to charge flow rates ob 1.2 to 2.5; (2) a stage of purifying and washing the low-purity p-xylene by recrystallization (-25.degree. to +10.degree. C.); (3) a stage of catalytic isomerization of the charge which has been p-xylene-depleted by the separating stage (1); and recovering an isomerate which si then recycled to the charge. The solvent for desorption in stage (1) and washing in stage (2) is advantageously toluene.

Abstract: The invention concerns, on one hand, a new zeolitic catalytic composition which comprises a small-pore mordenite present in the form of needles, exchanged with at least one metal chosen from the group consisting of cooper, vanadium, tungsten, iron, colbalt and molybdenum, and on the other hand, use of this catalytic composition as a catalyst for the reduction of nitrogen oxides by ammonia.

Abstract: Process for manufacturing a catalyst suitable for the hydrogenation and reforming reactions, comprising impregnating, at a temperature of a least 160.degree. C, a solid carrier, with a homogeneous catalyst solution obtained by admixing in a solvent, at a temperature above 100.degree.C, a salt of a metal whose atomic number is in the range of from 22 to 29, 40 to 47, 72 to 79 and 90 to 92, with a metallic or organo-metallic reducing agent, the metal component being selected from groups Ia, IIa, IIb and IIIb.