Para-xylene is separated from a mixture of C8 aromatics using a simulated moving bed (SMB) adsorption process, wherein a MOF is used as an adsorbent and an alkane or alkene having 7 or less carbon atoms, such as hexane or heptane is used as desorbent. Because of the difference in boiling points of a hexane or heptane desorbent as compared to conventional desorbents such as toluene or para-diethylbenzene, less energy is required to separate hexane or heptane from C8 aromatics by distillation than the energy required to separate toluene or diethylbenzene from C8 aromatics by distillation.

Processes and apparatuses for producing a C.sub.8 aromatic isomer product are provided. The apparatus comprises an isomerization unit to provide an isomerized stream. An isomerate stripper column is in communication with the isomerization unit to provide an isomerate stripper overhead stream comprising C.sub.6 hydrocarbons in an isomerate overhead line and an isomerate stripper bottoms stream in an isomerate bottoms line. A dividing wall naphthene splitter column is in communication with the isomerate bottoms line to provide an overhead naphthene splitter stream comprising the C.sub.8 naphthenes and C.sub.7 aromatic hydrocarbons in a naphthene splitter overhead line and a naphthene splitter sidedraw stream comprising C.sub.8 aromatic isomers in a naphthene splitter sidedraw line. An extractive distillation column is in communication with the naphthene splitter overhead line to provide a recycle feedstream comprising the C.sub.8 naphthenes in a recycle line and an extract stream comprising the C.sub.7 aromatic hydrocarbons in an extract line.

Processes and apparatuses for producing a C.sub.8 aromatic isomer product are provided. The apparatus comprises an isomerization unit to provide an isomerized stream. An isomerate stripper column is in communication with the isomerization unit to provide an isomerate stripper overhead stream comprising C.sub.6 hydrocarbons in an isomerate overhead line and an isomerate stripper bottoms stream in an isomerate bottoms line. A dividing wall naphthene splitter column is in communication with the isomerate bottoms line to provide an overhead naphthene splitter stream comprising the C.sub.8 naphthenes and C.sub.7 aromatic hydrocarbons in a naphthene splitter overhead line and a naphthene splitter sidedraw stream comprising C.sub.8 aromatic isomers in a naphthene splitter sidedraw line. An extractive distillation column is in communication with the naphthene splitter overhead line to provide a recycle feedstream comprising the C.sub.8 naphthenes in a recycle line and an extract stream comprising the C.sub.7 aromatic hydrocarbons in an extract line.

Processes for the energy efficient recycle of naphthenes in a paraxylene manufacturing process comprise partially condensing a reactor effluent and using a sidedraw tower apparatus. The naphthenes are efficiently separated into the sidedraw stream of the sidedraw tower apparatus. At least a portion of the sidedraw stream is directed to a paraxylene recovery section that produces a paraxylene product and a paraxylene lean stream comprising essentially all of the naphthenes in the sidedraw stream directed to the paraxylene recovery section. The paraxylene lean stream is recycled back to the reactor thereby preventing excessive loss of naphthenes from the processes.

Processes for the energy efficient recycle of naphthenes in a paraxylene manufacturing process comprise partially condensing a reactor effluent and using a sidedraw tower apparatus. The naphthenes are efficiently separated into the sidedraw stream of the sidedraw tower apparatus. At least a portion of the sidedraw stream is directed to a paraxylene recovery section that produces a paraxylene product and a paraxylene lean stream comprising essentially all of the naphthenes in the sidedraw stream directed to the paraxylene recovery section. The paraxylene lean stream is recycled back to the reactor thereby preventing excessive loss of naphthenes from the processes.

Processes and apparatuses for isomerizing hydrocarbons are provided. In an embodiment, a process for isomerizing hydrocarbons includes providing a first hydrocarbon feed that includes hydrocarbons having from 5 to 7 carbon atoms. The first hydrocarbon feed is fractionated to produce a first separated stream that includes hydrocarbons having from 5 to 6 carbon atoms and a second separated stream that includes hydrocarbons having 7 carbon atoms. The first separated stream is contacted with a benzene saturation catalyst at benzene saturation conditions to produce an intermediate stream and subsequently isomerized in the presence of a first isomerization catalyst and hydrogen under first isomerization conditions to produce a first isomerized stream. The second separated stream is isomerized in the presence of a second isomerization catalyst and hydrogen under second isomerization conditions that are different from the first isomerization conditions to produce a second isomerized stream.

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.

A process for the production of C.sub.4 olefins, which may include: contacting a hydrocarbon mixture comprising alpha-pentenes with an isomerization catalyst to form an isomerization product comprising beta-pentenes; contacting ethylene and the beta-pentenes with a first metathesis catalyst to form a first metathesis product comprising butenes and propylene, as well as any unreacted ethylene and C.sub.5 olefins; and fractionating the first metathesis product to for an ethylene fraction, a propylene fraction, a butene fraction, and a C.sub.5 fraction.

Methods for utilizing carbon dioxide to produce multi-carbon products are disclosed. The systems and methods of the present disclosure involve: reducing CO.sub.2 to produce a first product mixture comprising an alcohol product mixture comprising one or more alcohols and a paraffin product mixture comprising one or more paraffins; dehydrating the alcohol product mixture to form an olefin product mixture comprising one or more olefins; oligomerizing the olefin product mixture to form a higher olefin product mixture comprising unsaturated paraffins and optionally aromatics; and reducing the higher olefin product mixture to form a higher hydrocarbon product mixture comprising unsaturated paraffins and optionally aromatics. Catalyst materials and reaction conditions for individual steps are disclosed to optimize yield for ethanol or jet fuel range hydrocarbons.