Methods and systems for producing
A method for producing para-xylene (PX) includes introducing a C 8 aromatic-containing composition to a xylene rerun column to separate the C 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 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.
1. A method for producing para-xylene (PX), the method comprising:
separating a C 8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent, the xylene-containing effluent comprising para-xylene (PX), ethylbenzene (EB), and one or both of meta-xylene (MX) and ortho-xylene (OX);
recovering PX from the xylene-containing effluent in a PX recovery unit to produce a PX product and a PX-depleted stream comprising EB and one or both of MX and OX;
passing the PX-depleted stream to a membrane isomerization unit;
isomerizing at least a portion of the MX, the OX, or both in the PX-depleted stream to PX by contacting the portion of the MX, OX, or both with a catalytic membrane in the membrane isomerization unit to produce an isomerate;
passing the isomerate to a membrane separation unit;
subjecting the isomerate to the membrane separation unit to produce a permeate that is PX-rich and a retentate that is PX-lean;
passing the retentate to an EB dealkylation unit; and
dealkylating at least a portion of EB in the retentate in the EB dealkylation unit to produce a dealkylation effluent comprising one or more C 7− compounds.
2. The method of claim 1 , in which the membrane separation unit comprises a carbon-based membrane.
3. The method of claim 1 , in which the catalytic membrane in the membrane isomerization unit comprises an acidic sulfonated catalytic membrane.
4. The method of claim 1 , further comprising subjecting the dealkylation effluent to a separation process operable to separate at least a portion of the C 7− compounds from the dealkylation effluent.
5. The method of claim 4 , in which separating the C 7− compounds from the dealkylation effluent comprises passing the dealkylation effluent to a stripper.
6. The method of claim 1 , in which dealkylating the at least a portion of the EB comprises contacting the at least a portion of the EB with a dealkylation catalyst in the EB dealkylation unit.
7. The method of claim 1 , in which recovering PX includes subjecting the xylene-containing effluent to crystallization, selective adsorption, or combinations of these to recover the PX product.
8. The method of claim 1 , in which the PX product comprises at least 99.0 weight percent PX.
9. A method for producing para-xylene (PX), the method comprising:
separating a C 8 aromatic-containing composition into a xylene-containing effluent and a heavy effluent in a xylene rerun column, the xylene-containing effluent comprising para-xylene (PX), ethylbenzene (EB), and one or both of meta-xylene (MX) and ortho-xylene (OX);
recovering PX from at least a portion of the xylene-containing effluent in a PX recovery unit to produce a PX product and a PX-depleted effluent;
dealkylating at least a portion of EB in the PX-depleted effluent in an EB dealkylation unit to produce a dealkylation effluent comprising one or more C 7− compounds;
separating the dealkylation effluent into a C 7− effluent, an EB-depleted effluent, and a bottoms stream;
isomerizing at least a portion of the MX, the OX, or both in the EB-depleted effluent to PX in a membrane isomerization unit to produce an isomerate by contacting the portion of the MX, OX, or both with a catalytic membrane in the membrane isomerization unit; and
subjecting the isomerate to a membrane separation unit to produce a permeate that is PX-rich and a retentate that is PX-lean.
10. The method of claim 9 , in which the membrane isomerization unit comprises an acidic sulfonated catalytic membrane.
11. The method of claim 9 , in which the membrane separation unit comprises a carbon-based membrane.
12. The method of claim 9 , further comprising passing the xylene-containing effluent directly from the xylene rerun column to the PX recovery unit.
13. The method of claim 9 , in which the membrane separation unit is directly downstream of the xylene rerun column and the PX-recovery unit and the EB dealkylation unit are directly downstream of the membrane separation unit.
14. The method of claim 13 , further comprising:
combining the isomerate with the xylene-containing effluent upstream of the membrane separation unit;
subjecting the isomerate and the xylene-containing effluent to membrane separation in the membrane separation unit;
passing the permeate from the membrane separation unit to the PX recovery unit; and
passing the retentate to the EB dealkylation unit.
15. The method of claim 9 , further comprising combining the retentate with the PX-depleted effluent upstream of the EB dealkylation unit.
16. The method of claim 9 , further comprising passing the isomerate directly from the membrane isomerization unit to the membrane separation unit.
17. The method of claim 9 , further comprising passing the retentate from the membrane separation unit directly to the EB dealkylation unit.