Selective Toluene Disproportionation Conversion – GT-STDP℠

GT-STDP produces paraxylene-rich mixed xylene along with high purity benzene streams from toluene.  This toluene disproportionation technology boasts high toluene conversion rates and integrated production routes.  GT-STDP features a commercially-proven proprietary catalyst with high activity and selectivity to paraxylene.

Process Description

The technology encompasses three main processing areas: reactor section, product distillation and paraxylene (PX) recovery.  Fresh toluene and recycled toluene from the product distillation area are mixed with hydrogen.  The hydrogen-to-toluene ratio is about 1 to 1.5.  The mixed stream is heated against reactor effluent and through a process furnace.  The heated vapor stream flows to the reactor, which produces the benzene and xylenes.  The toluene disproportionation reactions are mildly exothermic.
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 recycle hydrogen purity.  The recycled hydrogen is then compressed, mixed with makeup hydrogen and returned to the reactor.
The liquid stream from the separator is pumped to the stripper to remove light hydrocarbons.  The liquid stream from the stripper bottoms contains benzene, toluene, mixed xylenes and a small quantity of C9+ aromatics.  This liquid stream is sent to the product distillation section to obtain benzene product, toluene for recycle to the reactor, mixed xylenes to the PX recovery section, and C9+ aromatics.  The PX in the mixed xylenes stream is over 90% purity, which permits low-cost crystallization technology to be used for the PX purification.

Process Advantages

  • Simple, low cost fixed-bed reactor design
  • Drop-in catalyst replacement for existing hydroprocessing reactors
  • Paraxylene enriched to over 90 percent in the xylene stream
  • On-specification benzene with traditional distillation
  • Physically stable catalyst
  • Low hydrogen consumption
  • Moderate operating parameters; catalyst can be used as replacement to traditional toluene disproportionation units, or in grass roots designs
  • Efficient heat integration scheme, reduced energy consumption
  • Turnkey package for high purity benzene and paraxylene production available from licensor