A method of recovering paraxylene in a crystallization zone. The crystallization zone includes at least two crystallization stages and two reslurry stages. The method provides for lower throughput through the crystallization zone, resulting in lower capital costs, reduced electricity in operating separation equipment, as well as reduced refrigeration duty.

A method of recovering paraxylene in a crystallization zone. The crystallization zone includes at least two crystallization stages and two reslurry stages. The method provides for lower throughput through the crystallization zone, resulting in lower capital costs, reduced electricity in operating separation equipment, as well as reduced refrigeration duty.

A method of recovering paraxylene in a crystallization zone. The crystallization zone includes at least two crystallization stages and two reslurry stages. The method provides for lower throughput through the crystallization zone, resulting in lower capital costs, reduced electricity in operating separation equipment, as well as reduced refrigeration duty.

A method of recovering paraxylene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxylene based on the cycling of partial pressure in the zone. A first hydrogen purge is fed concurrent to the feed. A second hydrogen purge is countercurrent to the feed.

A method of recovering paraxylene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxylene based on the cycling of partial pressure in the zone. A first hydrogen purge is fed concurrent to the feed. A second hydrogen purge is countercurrent to the feed.

A method of recovering paraxyiene in a pressure swing adsorption unit with varying hydrogen purge pressures. The pressure swing adsorption zone is adapted to adsorb and desorb paraxyiene based on the cycling of partial pressure in the zone. A first hydrogen purge fed to the zone is within 50 psi of the adsorption pressure of paraxyiene in the zone. A second hydrogen purge fed to the zone is within 50 psi of the desorption pressure of paraxyiene in the zone. The overall amount of hydrogen necessary to operate the pressure swing adsorption zone is reduced and heat may be recovered from the effluent leaving the pressure swing adsorption zone.

A method for producing para-xylene (PX) includes introducing a C.sub.8 aromatic-containing composition to a xylene rerun column to separate the C.sub.8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent and passing the xylene-containing effluent to a PX processing loop that includes a PX recovery unit operable to separate a PX product from the xylene-containing effluent, a membrane isomerization unit operable to convert a portion of the MX, OX, or both from the xylene-containing effluent to PX, an EB dealkylation unit operable to dealkylate EB from the xylene-containing effluent to produce benzene, toluene, and other C.sub.7− compounds, and a membrane separation unit operable to produce a permeate that is PX-rich and a retentate that is PX-lean. The permeate is passed to the PX recovery unit for recovery of PX, which the retentate is bypassed around the PX recovery unit circulated through the xylene processing loop.

A method for producing para-xylene (PX) includes introducing a C.sub.8 aromatic-containing composition to a xylene rerun column to separate the C.sub.8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent and passing the xylene-containing effluent to a PX processing loop that includes a PX recovery unit operable to separate a PX product from the xylene-containing effluent, a membrane isomerization unit operable to convert a portion of the MX, OX, or both from the xylene-containing effluent to PX, an EB dealkylation unit operable to dealkylate EB from the xylene-containing effluent to produce benzene, toluene, and other C.sub.7− compounds, and a membrane separation unit operable to produce a permeate that is PX-rich and a retentate that is PX-lean. The permeate is passed to the PX recovery unit for recovery of PX, which the retentate is bypassed around the PX recovery unit circulated through the xylene processing loop.

In the present method a reaction mixture is comprised of a source of adamantane, mixed with an alkane or cycloalkane. A Lewis acid catalyst is added to the reaction mixture which is heated and then purified. The resulting alkyl diamondoid mixtures have significantly higher densities and volumetric net heats of combustion while maintaining low viscosities which allow for use at low temperature.

In the present method a reaction mixture is comprised of a source of adamantane, mixed with an alkane or cycloalkane. A Lewis acid catalyst is added to the reaction mixture which is heated and then purified. The resulting alkyl diamondoid mixtures have significantly higher densities and volumetric net heats of combustion while maintaining low viscosities which allow for use at low temperature.