Xylenes and Benzene Process by China Petrochemical Technology

The S-TDT process can produce mixed xylenes and benzene in an aromatics complex through disproportionation of toluene and transalkylation of toluene and C9+ aromatics (C9+ A) using toluene
and C9+ A as feedstocks.

The commercially proven HAT series catalysts are the core of the S-TDT process. The catalyst provides high activity, high selectivity, good operation stability and feedstock flexibility. The excellent performance of HAT series catalysts provides technological supports for some aromatics complexes to expand their capacities without a reactor revamp, increase in catalyst inventory and hydrogen compressor replacement.

Commercial examples: The capacities for two plants were 398,000 metric tpy and 1.007 million metric tpy, respectively. After using the HAT catalysts and operation conditions of the S-TDT process, outputs for both benzene and mixed xylenes increased by 40% without any changes to the reactor, compressor and catalyst inventory for both facilities.

Either pure toluene or high content of C9+ A (70 wt%) can be used as feedstocks for the process. In particular, C10 aromatics (C10A) in the feedstock can be as much as 10 wt%. C10A can also be converted into lower carbon aromatics, so that more benzene and mixed-xylenes can be produced and plant profitability is increased.

The purity of the benzene product from the benzene and toluene (BT) fractionation section is such that no further extraction is needed. The mixed-xylenes product containing only 1%–4% ethylbenzene is a good feedstock for paraxylene (PX) production.

To reduce operating costs and save energy, the plant’s waste heat is utilized as much as possible with heat integration technology and high-efficiency heat exchangers.

Licensor: China Petrochemical Technology Co., Ltd.

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