The UOP PX-Plus XP Process converts toluene to paraxylene and benzene. The paraxylene is purified to 99.9+ wt% via
single-stage crystallization and a wash column. The benzene purity is 545-grade by fractionation.
The PX-Plus XP Process is composed of three processing steps:
(1) Selective toluene disproportionation, via the PX-Plus Process
(2) Fractionation for recovery of recycle toluene and benzene product
(3) The Badger/Niro paraxylene crystallization process, where single-stage crystallization and crystal wash columns are used.
In the PX-Plus technology, fresh toluene is combined with recycle gas, heated and fed to a fixed-bed reactor. The paraselective catalyst produces xylene product with 90% paraxylene in the xylenes. Reactor effluent flows to a separator, where the recycle gas is recovered, and the liquid product is sent to a stripper.
In the fractionation section, stripper bottoms are fed to a benzene column, where the benzene product is recovered and the unconverted toluene is fractionated for recycle. The toluene column bottoms are sent to a rerun column where the paraxylene concentrated fraction is taken overhead.
In the Badger/Niro crystallization unit, the xylenes are fed to a single-stage crystallization section that uses continuous suspension crystallization. In this section, the paraxylene is purified with a single refrigerant compressor system, and the mother liquor rejected. The purified paraxylene is fed to a Niro wash column section where ultra-high-purity paraxylene is produced by countercurrent crystal washing.
Components of this flexible technology are especially suited for capacity expansion of existing paraxylene production facilities.