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AssigneeInstitut Francais du Petrole
InventorsPaul Mikitenko, Stuart R MacPherson
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A process for producing paraxylene of very high purity from a charge containing a mixture of aromatic hydrocarbons having 7 to 9 carbon atoms in which at least a portion of the charge is made to circulate in a zone suited to enrich a first fraction of paraxylene and at least a portion of said first fraction is purified by at least one high-temperature crystallization in at least one crystallization zone, the process being characterized in that said first paraxylene-enriched fraction is crystallized in a crystallization zone comprising at least two crystallization stages (50,70) at high temperature, and advantageously between +10 and -25 .degree. C. The paraxylene enriching zone can be a crystallization at very low temperature, a selective adsorption or a toluene disproportionation zone.
A process for the production of paraxylene of very high purity from a charge containing a mixture of aromatic hydrocarbons having 7 to 9 carbon atoms, comprising circulating at least a portion of the charge in an enrichment zone to produce a first fraction with paraxylene, purifying at least a portion of said first fraction in a purification zone by at least one crystallization in at least one crystallization zone, said crystallization zone comprising at least two crystallization stages at a temperature between +50 and -22.degree. F., and covering paraxylene crystals from each crystallization stage.
A process for the production of paraxylene of very high purity from a charge containing a mixture of aromatic hydrocarbons having 7 to 9 carbon atoms, comprising performing a first crystallization of a paraxylene-enriched fraction, having a paraxylene content of at least 50% by weight, and of optionally melted recyled crystals coming from a second crystallization in a first high temperature crystallization zone at a temperature T1, recovering a suspension of paraxylene crystals in a first mother liquor, separating the crystals from the first mother liquor in a first separation zone, washing said crystals, melting said crystals and recovering a stream of melted paraxylene, crystallizing at least a portion of the first mother liquor in a second high temperature crystallization zone at a temperature T2 that is lower than temperature T1, recovering a suspension of second paraxylene crystals in a second mother liquor, separating the second crystals from the second mother liquor in a second separation zone, recovering a second mother liquor, and second crystals, optionally melting a portion of the second crystals and recycling the optionally melted second melted crystals to the first crystallization zone and recrystallizing the melted crystals with the paraxylene-enriched fraction at a temperature T1.
Dependencies are inferred from the claim text.