DX process converts ethylbenzene (EB) contained in the C8 aromatics feedstocks to high-purity benzene plus ethane and upgrades mixed xylenes to premium grade. The feedstocks can be either pygas C8 or reformer C8 streams. The technology features a proprietary catalyst with high activity, low ring loss and superior long catalyst cycle length. This technology is partnered with Toray Industries, Inc.
The technology encompasses two main processing areas: reactor section and product distillation section. In this process, C8 aromatics feed stream is first mixed with hydrogen. The mixed stream is then heated against reactor effluent and sent through a process furnace. The heated mixture is fed into the DX reaction unit, where EB is de-alkylated at very high conversion and xylenes are isomerized to equilibrium.
The reactor effluent is cooled and flows to the separator, where the hydrogen-rich vapor phase is separated from the liquid stream. A small portion of the vapor phase is purged to control the recycle hydrogen purity. The recycle hydrogen is then compressed, mixed with makeup hydrogen and returned to the reactor.
The liquid stream from the separator is pumped to the deheptanizer to remove light hydrocarbons. The liquid stream from the deheptanizer overhead contains benzene and toluene and is sent to distillation section to produce high-purity benzene and toluene products. The liquid stream from the deheptanizer bottoms contains mixed xylenes and a small amount of C9+ aromatics. This liquid stream is sent to the PX recovery section. The mixed xylenes stream is very low in EB due to high EB conversion in the DX reactor, which debottlenecks the PX recovery unit.
Process advantages:
• Simple, low cost fixed-bed reactor design
• Flexible feedstocks and operation
• High EB conversion per pass can be nearly 100wt%
• DX products are isomerized to equilibrium composition of xylene, which unloads the isomerization unit
• Low ring loss at very high EB conversion
• On-specification benzene with traditional distillation
• Extremely stable catalyst
• Low hydrogen consumption
• Moderate operating parameters
• Efficient heat integration scheme reduces energy consumption
• Turnkey package for high-purity benzene, toluene and PX production available from licensor.
Licensor: GTC Technology.
