Asymmetric membrane structures are provided that are suitable for hydrocarbon reverse osmosis of small hydrocarbons. Separation of para-xylene from ortho- and meta-xylene is an example of a separation that can be performed using hydrocarbon reverse osmosis. Hydrocarbon reverse osmosis separations can be incorporated into a para-xylene isomerization and recovery system in a variety of manners.

Asymmetric membrane structures are provided that are suitable for hydrocarbon reverse osmosis of small hydrocarbons. Separation of para-xylene from ortho- and meta-xylene is an example of a separation that can be performed using hydrocarbon reverse osmosis. Hydrocarbon reverse osmosis separations can be incorporated into a para-xylene isomerization and recovery system in a variety of manners.

In a process for producing one or more 3,3-, 3,4- and 4,4-dimethyl biphenyl isomers, a feed comprising toluene is contacted with hydrogen in the presence of a hydroalkylation catalyst under conditions effective to produce a hydroalkylation reaction product comprising (methylcyclohexyl)toluenes. At least part of the hydroalkylation reaction product is dehydrogenated in the presence of a dehydrogenation catalyst under conditions effective to produce a dehydrogenation reaction product comprising a mixture of dimethyl biphenyl isomers. The dehydrogenation reaction product is then separated into at least a first stream containing one or more 3,3-, 3,4- and 4,4-dimethyl biphenyl isomers and at least one second stream comprising one or more 2,X-dimethyl biphenyl isomers (where X is 2, 3, or 4). The 3,3-, 3,4- and 4,4-dimethyl biphenyl isomers are then separated utilizing selective adsorption.

Processes and apparatuses for producing para-xylenes are provided. The processes comprises providing a hydrocarbon stream comprising C7+ hydrocarbons. The hydrocarbon stream is separated to provide a C8 aromatics stream and an ortho-xylene rich stream. The C8 aromatics stream is passed to a para-xylene separation unit for separating para-xylene to provide a para-xylene stream and a raffinate stream. At least a portion of the raffinate stream is passed to a first isomerization unit to provide a first isomerization effluent, wherein the first isomerization effluent is produced in the presence of an ethylbenzene (EB) isomerization catalyst. At least a portion of the ortho-xylene rich stream is contacted with an isomerization catalyst in a second isomerization unit in liquid phase at isomerization conditions in substantial absence of hydrogen to produce a second isomerization effluent.

Processes and apparatuses for producing para-xylenes are provided. The processes comprises providing a hydrocarbon stream comprising C7+ hydrocarbons. The hydrocarbon stream is separated to provide a C8 aromatics stream and an ortho-xylene rich stream. The C8 aromatics stream is passed to a para-xylene separation unit for separating para-xylene to provide a para-xylene stream and a raffinate stream. At least a portion of the raffinate stream is passed to a first isomerization unit to provide a first isomerization effluent, wherein the first isomerization effluent is produced in the presence of an ethylbenzene (EB) isomerization catalyst. At least a portion of the ortho-xylene rich stream is contacted with an isomerization catalyst in a second isomerization unit in liquid phase at isomerization conditions in substantial absence of hydrogen to produce a second isomerization effluent.

This invention relates to a method of separating an isomerization zone effluent mixture comprising between 5 and 8 carbon atoms into high octane isomerate product streams and low octane streams which may be recycled to the isomerization zone. The separation process makes use of a dividing wall column to efficiently perform the separation of high octane multibranched paraffins from low octane straight chain and single branched paraffins.

This invention relates to a method of separating an isomerization zone effluent mixture comprising between 5 and 8 carbon atoms into high octane isomerate product streams and low octane streams which may be recycled to the isomerization zone. The separation process makes use of a dividing wall column to efficiently perform the separation of high octane multibranched paraffins from low octane straight chain and single branched paraffins.

In a process for producing para-xylene, at least one feed comprising C.sub.6+ aromatic hydrocarbons is supplied to a dividing wall distillation column to separate the feed into a C.sub.7 aromatic hydrocarbon-containing stream, a C.sub.8 aromatic hydrocarbon-containing stream and a C.sub.9+ aromatic hydrocarbon-containing stream. At least part of the C.sub.8 aromatic hydrocarbon-containing stream is then supplied to a para-xylene recovery unit to recover para-xylene from the C.sub.8 aromatic hydrocarbon-containing stream and produce a para-xylene depleted stream. The para-xylene depleted stream is contacted with a xylene isomerization catalyst in a xylene isomerization zone under conditions effective to isomerize xylenes in the para-xylene depleted stream and produce an isomerized stream, which is then at least partially recycled to the para-xylene recovery unit.

In a process for producing para-xylene, at least one feed comprising C.sub.6+ aromatic hydrocarbons is supplied to a dividing wall distillation column to separate the feed into a C.sub.7 aromatic hydrocarbon-containing stream, a C.sub.8 aromatic hydrocarbon-containing stream and a C.sub.9+ aromatic hydrocarbon-containing stream. At least part of the C.sub.8 aromatic hydrocarbon-containing stream is then supplied to a para-xylene recovery unit to recover para-xylene from the C.sub.8 aromatic hydrocarbon-containing stream and produce a para-xylene depleted stream. The para-xylene depleted stream is contacted with a xylene isomerization catalyst in a xylene isomerization zone under conditions effective to isomerize xylenes in the para-xylene depleted stream and produce an isomerized stream, which is then at least partially recycled to the para-xylene recovery unit.

Systems and methods are provided for converting alkane while generating improved yields of desirable aromatics and/or improved selectivity for forming desired aromatics, such as para-xylene (p-xylene). Aromatics generated during the aromatic formation process can be alkylated to form xylenes with improved yield and/or improved selectivity.