Asymmetric membrane structures are provided that are suitable for various types of separations, such as separations by reverse osmosis. Methods for making an asymmetric membrane structure are also provided. The membrane structure can include at least one polymer layer. Pyrolysis can be used to convert the polymer layer to a porous carbon structure with a higher ratio of carbon to hydrogen.

Asymmetric membrane structures are provided that are suitable for various types of separations, such as separations by reverse osmosis. Methods for making an asymmetric membrane structure are also provided. The membrane structure can include at least one polymer layer. Pyrolysis can be used to convert the polymer layer to a porous carbon structure with a higher ratio of carbon to hydrogen.

In a process for separating dimethyl biphenyl isomers a mixture comprising one or more 3,3, 3,4- or 4,4-dimethyl biphenyl isomers, one or more 2,X-dimethyl biphenyl isomers (where X=2, 3, or 4) and one or more further hydrocarbon components is contacted with a first adsorbent, thereby selectively adsorbing one or more of the dimethyl biphenyl isomers within the first adsorbent. A first raffinate stream containing less selectively adsorbed components is withdrawn from the first adsorbent and a first extract stream containing selectively adsorbed dimethyl biphenyl isomers is withdraw. The selectively adsorbed dimethyl biphenyl isomers comprise one or more of 3,3-, 3,4- or 4,4-dimethyl biphenyl isomers and one or more of 2,X-dimethyl biphenyl isomers (where X=2, 3, or 4).

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.

A process for separating dimethyl biphenyl (DMBP) isomers, including contacting a mixture of 3,3-DMBP, 3,4-DMBP and 4,4-DMBP in a first solvent with a 12-member ring zeolite exchanged with potassium or barium, or combinations thereof, and adsorbing the 3,3-DMBP onto the 12-member ring zeolite, such as by passing the mixture through at least one packed bed of the potassium and/or barium exchanged 12-member ring zeolite.

Methods and processes for producing paraxylene from catalytic cracking hydrocarbons, particularly C.sub.4 and C.sub.5+ streams, are disclosed. Each of the processing steps may be tailored to the overall objective of high paraxylene yield from a relative inexpensive feedstock.

Methods and processes for producing paraxylene from catalytic cracking hydrocarbons, particularly C.sub.4 and C.sub.5+ streams, are disclosed. Each of the processing steps may be tailored to the overall objective of high paraxylene yield from a relative inexpensive feedstock.

Processes for reforming and transalkylating hydrocarbons are disclosed. A method for processing a hydrocarbon stream includes the steps of separating para-xylene from a first mixed-xylene and ethylbenzene-containing stream to produce a first non-equilibrium xylene and ethylbenzene stream and isomerizing the first non-equilibrium xylene and ethylbenzene stream to produce additional para-xylene. The method further includes transalkylating a toluene stream to produce a second mixed-xylene and ethylbenzene-containing stream, separating para-xylene from the second mixed-xylene and ethylbenzene-containing stream to produce a second non-equilibrium xylene and ethylbenzene stream, and isomerizing the second non-equilibrium xylene and ethylbenzene stream using a liquid phase isomerization process to produce additional para-xylene.

The present invention relates to heavy desorbent and light desorbent aromatics complex flow scheme. More particularly, this invention relates to the integration of a dual raffinate para-xylene separation process with two isomerization zones. The first isomerization zone is a liquid phase isomerization zone and the second isomerization zone is either an ethylbenzene isomerization zone, or an isomerization zone using MAPSO-31.

Systems and methods are provided for forming para-xylene from aromatics-containing streams having reduced or minimized amounts of C.sub.2+ side chains. Reduced or minimized amounts of C.sub.2+ side chains can provide benefits for improving and/or allowing modification of transalkylation conditions, xylene isomerization conditions, or a combination thereof. Such aromatics-containing streams can be formed, for example, by conversion of methyl halide, methanol, syngas, and/or dimethyl ether to aromatics by an aromatic conversion process. The methyl halide, methanol, syngas, and/or dimethyl ether can be formed by conversion of methane.