Xylene isomers
원료
C8 aromatics
생산물
xylene isomers
적용
To produce a desired xylene isomer (or isomers) from a mixture of C8 aromatics using the Isomar process
설명
Description:
The reactor (1) catalytically converts any nonequilibrium mixture of a C8 aromatics toward an equilibrum composition. Then the desired products, usually para- and orthoxylene, are removed from the reactor effluent, and the resultion nonequilibrium mixture is recycled to the Isomer unit.
Product purity depends primarily on the separation procedures involved. For this flow diagram, the hydrogen-rich recycle gas stream is separated (2) before the reactor's liquid effluent is fractionated (3) to remove light cracked byproducts overhead. The remaining C8 aromatics enter the xylene splitter (4). Bottoms from the splitter are separated (5) into an overhead product of o-xylene and byproduct bottoms stream of C9 and heavier aromatics.
The overhead from the splitter (4) enters a UOP Parex process unit (6) for the recovery of p-xylene. The remaining products are recycled to the reactor. The high purity of p-xylene results from the efficiency of the Parex unit. The high purity of o-xylene is controlled by efficient fractionation and feedstock composition.
Fresh feed to the Isomar unit enters ahead of the xylene splitter (4). The feed may be C8 aromatic mixture derived from, for example, catalytic reformate, hydrotreated pyrolysis gasoline, or an LPG aromatization unit. The feed may contain up to 40% ethylbenzene, which is converted to xylenes at a high conversion rate per pass. Feedstocks may be pure solvent extracts or fractional heartcuts containing as high as 25% saturates. Hydrogen supply may be from catalytic reforming or any other suitable source. Chemical hydrogen consumption is minimal.
Product purity depends primarily on the separation procedures involved. For this flow diagram, the hydrogen-rich recycle gas stream is separated (2) before the reactor's liquid effluent is fractionated (3) to remove light cracked byproducts overhead. The remaining C8 aromatics enter the xylene splitter (4). Bottoms from the splitter are separated (5) into an overhead product of o-xylene and byproduct bottoms stream of C9 and heavier aromatics.
The overhead from the splitter (4) enters a UOP Parex process unit (6) for the recovery of p-xylene. The remaining products are recycled to the reactor. The high purity of p-xylene results from the efficiency of the Parex unit. The high purity of o-xylene is controlled by efficient fractionation and feedstock composition.
Fresh feed to the Isomar unit enters ahead of the xylene splitter (4). The feed may be C8 aromatic mixture derived from, for example, catalytic reformate, hydrotreated pyrolysis gasoline, or an LPG aromatization unit. The feed may contain up to 40% ethylbenzene, which is converted to xylenes at a high conversion rate per pass. Feedstocks may be pure solvent extracts or fractional heartcuts containing as high as 25% saturates. Hydrogen supply may be from catalytic reforming or any other suitable source. Chemical hydrogen consumption is minimal.
Operating conditions: Temperature and pressures are moderate, permitting the use of carbon and low-alloy steel and conventional equipment. Typical operating pressure for a modern new unit is 130 psig at a temperature of 730℉.
Yields:
A typical mass balance is as follows:
| Composition Ethybenzene p-Xylene m-Xylene o-Xylene |
Fresh feed, wt units 25.5 14.0 41.0 19.5 |
Product, wt units - 70.6 - 19.6 |
