The Paraxylene (PX) production unit consists of three subunits. Mixed Xylene (MX) from the MX unit is fed into the Parex unit to separate paraxylene from other xylene compounds through an adsorption process. The resulting paraxylene is then distilled to achieve a purity of up to 99.7% by weight. The remaining xylene compounds, referred to as the raffinate stream, include ortho-xylene, meta-xylene, and ethylbenzene. These are sent to the Isomar unit, where ortho-xylene and meta-xylene are converted into paraxylene through isomerization, while ethylbenzene is transformed into benzene via the EB dealkylation reaction, resulting in increased production of both paraxylene and benzene by-products.

Additionally, the Xylene Rerun Unit separates heavy aromatics (C9+) from light aromatics (C8) in the mixed xylene, preparing it for the Parex unit. Some C9+ aromatics from the MX unit are processed in the Xylene Rerun Unit to isolate A9, which is then returned to Thai Oil Public Company Limited for gasoline blending. The remaining heavy components, known as “Heavies,” are also sent back to Thai Oil Public Company Limited for fuel oil blending.

The Separation Unit for Aromatics and Non-Aromatics (ED Sulfolane) receives crude benzene from the MX unit and benzene from the Isomar unit to extract non-aromatic compounds using a solvent. The extracted non-aromatic compounds are then sent back to Thaioil Public Company Limited for use in gasoline blending. Meanwhile, the remaining aromatic compounds are sent to the Benzene and Toluene Separation Unit (BTF-1) for further processing.

The Benzene & Toluene Fractionation 1 (BTF-1) unit receives aromatic compounds from the ED Sulfolane unit to separate benzene, toluene, and xylene, resulting in high-purity benzene and toluene for distribution to customers. Additionally, toluene can be sent to the PxMax unit for further production of paraxylene and benzene. Any remaining xylene is directed to the Xylene Rerun Unit for further processing.

The PxMax unit employs specialized technology designed to enhance the value of toluene by converting it into high-value paraxylene and benzene, which are key feedstocks for the petrochemical industry. Toluene entering the PxMax unit undergoes Selective Toluene Disproportionation (STDP) using specially structured molecular sieve catalysts to produce a xylene mixture rich in high-purity paraxylene and co-produced benzene. This technology allows the PxMax unit to generate xylene mixtures in high proportions while producing minimal gas byproducts. The byproduct gas is utilized as fuel within the complex, while the remaining xylene, benzene, and toluene are routed to the Benzene & Toluene Fractionation 2 Unit (BTF-II) for further processing.

The Benzene & Toluene Fractionation Unit 2 (BTF-II) receives the remaining mixed xylenes, benzene, and toluene from the PxMax unit for further fractionation. In this unit, benzene is purified to a sufficient degree for distribution to customers. The mixed xylene with a high paraxylene content is sent to the Parex unit to separate high-purity paraxylene for subsequent distribution. Finally, the remaining toluene is recycled back to the PxMax unit for further reactions.