Tatoray™ unit

The aromatics complex converts approximately 75% of the feed naphtha to petrochemical aromatics with the vast majority of the remainder being exported as raffinate and some hydrogen. With a modern aromatics complex flowscheme, a little over half of the mixed xylenes are produced in the Tatoray unit while the rest are produced in the CCR Platforming unit directly from the naphtha reforming. Having reviewed the framework of an aromatics complex we are now in a better position to understand the context of the continuous countercurrent liquid adsorptive Parex process which produces the primary aromatics complex product, p-xylene. 

Combined mixed xylenes from the CCR Platforming and Tatoray units make up the fresh feed to the Parex unit and Isomar unit loop. A typical composition... 

Commercial plants UOP has licensed a total of 44 Tatoray units 40 of these units are in operation and 4 are in various stages of construction. 

Toluene is usually blended with C9+ aromatics (Ag+) from the overhead of the heavy aromatics column (7) and charged to a Tatoray unit (8) for production of additional xylenes and benzene. Toluene and heavy aromatics can also be charged to a THDA unit (9) for production of additional benzene. 

Commercial plants UOP is the world s leading licensor of process technology for aromatics production. UOP has licensed more than 600 separate process units for aromatics production, including over 200 CCR Platforming units, 134 Sulfolane units, 80 Parex units, 61 Isomar units, 44 Tatoray units and 38 THDA units. 

Table 4. Tatoray Transalkylation of Toluenes and Aromatic Compounds, Relative Wt Units...

After the cmde BTX is formed, by reforming in this case, a heart cut is sent to extraction. Actually, the xylenes and heavier components are often sent to downstream processes without extraction. The toluene produced is converted to ben2ene, a more valuable petrochemical, by mnning it through a hydrodealkylation unit. This catalytic unit operates at 540—810°C with an excess of hydrogen. Another option is to disproportionate toluene or toluene plus aromatics to a mixture of ben2ene and xylenes using a process such as UOP s Tatoray or Mobil s Selective Toluene Disproportionation Process (STDP) (36). 

Tatoray [Transalkylation aromatics Toray] A process for transalkylating toluene, and/or trimethylbenzenes, into a mixture of benzene and xylenes. Operated in the vapor phase, with hydrogen, in a fixed bed containing a zeolite catalyst. Developed jointly by Toray Industries and UOP and now licensed by UOP. First operated commercially in Japan in 1969 as of 1992, 23 units were operating and 6 more were in design and construction. 

The Tatoray process unit is capable of processing feedstocks ranging from 100 wt% toluene to 100 wt% Ag+. The optimal concentration of Ag+ in the feed is typically 40-60 wt%. The Tatoray process provides an ideal way to produce additional mixed xylenes from toluene and heavy aromatics. 

Economics The process is designed to function at a much higher level of conversion per pass. This high conversion minimizes the size of the BT columns, and the size of Tatoray process unit, as well as the utility consumption of all of these units. Estimated ISBL costs based on a unit processing feed capacity of 355,000 mtpy (US Gulf Coast site in 2003) ... 

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