Disclosed is a process for recovering paraxylene in which a first simulated moving bed adsorption unit is used to produce two extract streams—one rich in paraxylene and a paraxylene-rich extract stream that is lean in ethylbenzene and an ethylbenzene-rich extract stream that is lean in paraxylene- and a paraxylene-depleted raffinate stream. A significant amount of the ethylbenzene is removed in the ethylbenzene-rich extract stream (at least enough to limit buildup in the isomerization loop), so the paraxylene-depleted raffinate stream may be isomerized in the liquid phase. Avoiding vapor phase isomerization saves energy and capital, as liquid phase isomerization requires less energy and capital than the vapor phase isomerization process due to the requirement of vaporizing the paraxylene-depleted stream and the use of hydrogen, which requires an energy and capital intensive hydrogen recycle loop.

Disclosed is a process for recovering paraxylene in which a first simulated moving bed adsorption unit is used to produce two extract streams—one rich in paraxylene and a paraxylene-rich extract stream that is lean in ethylbenzene and an ethylbenzene-rich extract stream that is lean in paraxylene- and a paraxylene-depleted raffinate stream. A significant amount of the ethylbenzene is removed in the ethylbenzene-rich extract stream (at least enough to limit buildup in the isomerization loop), so the paraxylene-depleted raffinate stream may be isomerized in the liquid phase. Avoiding vapor phase isomerization saves energy and capital, as liquid phase isomerization requires less energy and capital than the vapor phase isomerization process due to the requirement of vaporizing the paraxylene-depleted stream and the use of hydrogen, which requires an energy and capital intensive hydrogen recycle loop.

A method for recovering paraxylene from a mixture of aromatic hydrocarbons. The process uses a pressure swing adsorption zone followed by a paraxylene recovery zone. The invention provides for lower throughput through the paraxylene recovery zone, resulting in lower capital costs and operating costs.

A method for recovering paraxylene from a mixture of aromatic hydrocarbons. The process uses a pressure swing adsorption zone followed by a paraxylene recovery zone. The invention provides for lower throughput through the paraxylene recovery zone, resulting in lower capital costs and operating costs.

A method of producing p-xylene comprising the steps of separating the reformate feed in the reformate splitter to produce a benzene stream, a combined heavy stream, a xylene stream, and a toluene stream, converting the C9+ aromatic hydrocarbons in the presence of a dealkylation catalyst in the dealkylation reactor to produce a dealkylation effluent, separating the dealkylation effluent in the dealkylation splitter to produce a C9 stream and a C10+ stream, reacting the C9 stream, the toluene stream, the benzene stream, and the hydrogen stream in the presence of a transalkylation catalyst in the transalkylation reactor to produce a transalkylation effluent, separating the p-xylenes from the xylene stream in the p-xylene separation unit to produce a p-xylene product and a p-xylene depleted stream, converting the m-xylene and o-xylene in the p-xylene depleted stream in the isomerization unit to produce an isomerization effluent.

A method of producing p-xylene comprising the steps of separating the reformate feed in the reformate splitter to produce a benzene stream, a combined heavy stream, a xylene stream, and a toluene stream, converting the C9+ aromatic hydrocarbons in the presence of a dealkylation catalyst in the dealkylation reactor to produce a dealkylation effluent, separating the dealkylation effluent in the dealkylation splitter to produce a C9 stream and a C10+ stream, reacting the C9 stream, the toluene stream, the benzene stream, and the hydrogen stream in the presence of a transalkylation catalyst in the transalkylation reactor to produce a transalkylation effluent, separating the p-xylenes from the xylene stream in the p-xylene separation unit to produce a p-xylene product and a p-xylene depleted stream, converting the m-xylene and o-xylene in the p-xylene depleted stream in the isomerization unit to produce an isomerization effluent.

The present invention describes a process for obtaining para-xylene from a feedstock containing xylenes, ethylbenzene and C9+ hydrocarbons, said process comprising a single stage A of separation in a simulated moving bed carried out with a zeolite as adsorbent and a desorbent and making it possible to obtain at least three fractions, a fraction A1 comprising a mixture of para-xylene and of desorbent and two fractions A21, A22 comprising ethylbenzene (EB), ortho-xylene (OX) and meta-xylene (MX) and desorbent, said stage is carried out at a temperature between 20° C. and 250° C., under a pressure between the bubble pressure of the xylenes at the operating temperature and 2.0 MPa, and with a ratio by volume of the desorbent to the feedstock in the unit for separation 2 in a simulated moving bed is between 0.4 and 2.5, a stage B of fractionation by distillation in a 2-cut distillation column of the fractions A21 and A22 resulting from stage A, in which said fractions are introduced separately at distinct injection points, and makes it possible to obtain a fraction B2 containing ethylbenzene, ortho-xylene and meta-xylene, and a fraction B42 devoid of aromatic compounds having 8 carbon atoms and containing desorbent.

In a process for producing para-xylene, a feed stream comprising C.sub.6+ aromatic hydrocarbons is separated into a toluene-containing stream, a C.sub.8 aromatic hydrocarbon-containing stream and a C.sub.9+ aromatic hydrocarbon-containing stream. The toluene-containing stream is contacted with a methylating agent to convert toluene to xylenes and produce a methylated effluent stream. Para-xylene is recovered from the C.sub.8 aromatic hydrocarbon-containing stream and the methylated effluent stream in a para-xylene recovery section to produce a para-xylene depleted stream, which is then contacted with a xylene isomerization catalyst under liquid phase conditions effective to isomerize xylenes in the para-xylene depleted stream and produce an isomerized stream. The C.sub.9+-containing stream with a transalkylation catalyst under conditions effective to convert C.sub.9+-aromatics to C.sub.8−-aromatics and produce a transalkylated stream, which is recycled together with the isomerized stream to the para-xylene recovery section.

The invention relates to a p-xylene separation process wherein at least a portion of ethylbenzene present in an aromatics-containing feed is removed prior to isomerization. Aspects of the invention provide a process for producing p-xylene. The process includes providing a first mixture comprising ≧5.0 wt. % of aromatic C.sub.8 isomers, the C.sub.8 isomers comprising p-xylene and ethylbenzene. A p-xylene-containing portion and an ethylbenzene-containing portion are separated from the first mixture in a first separation stage to form a p-xylene-depleted raffinate. The first separation stage can include at least one simulated moving-bed adsorptive separation stage. At least a portion the p-xylene-depleted raffinate in the liquid phase is reacted to produce a reactor effluent comprising aromatic C.sub.8 isomers. The first mixture can be combined with ≧50.0 wt. % of the reactor effluent's aromatic C.sub.8 isomers. The combining can be carried out before and/or during the separating of the p-xylene and ethylbenzene portions.

The invention relates to a p-xylene separation process wherein at least a portion of ethylbenzene present in an aromatics-containing feed is removed prior to isomerization. Aspects of the invention provide a process for producing p-xylene. The process includes providing a first mixture comprising ≧5.0 wt. % of aromatic C.sub.8 isomers, the C.sub.8 isomers comprising p-xylene and ethylbenzene. A p-xylene-containing portion and an ethylbenzene-containing portion are separated from the first mixture in a first separation stage to form a p-xylene-depleted raffinate. The first separation stage can include at least one simulated moving-bed adsorptive separation stage. At least a portion the p-xylene-depleted raffinate in the liquid phase is reacted to produce a reactor effluent comprising aromatic C.sub.8 isomers. The first mixture can be combined with ≧50.0 wt. % of the reactor effluent's aromatic C.sub.8 isomers. The combining can be carried out before and/or during the separating of the p-xylene and ethylbenzene portions.