Also known as:
The BTX plant separates aromatics (Benzene, Toluene, Xylene) from reformate for use as petrochemical feed stocks. Pygas from an ethylene cracker can also be a feed stock for BTX units. The plant may also include units to convert toluene to benzene and xylene, and to convert mixed xylenes to P-xylene
The BTX plant is typically comprised of a number of units. These include:
Reformate splitter - A fractionator that splits the reformate into two fractions based on their boiling points. Most commonly the C7 and lighter material (containing benzene and toluene) will be the overhead and C8+ (containing the xylenes) will be in the bottoms.
Aromatics extraction unit (Sulfolane) - A solvent extraction process that removes aromatics from reformate or a reformate fraction. Currently it is more common to use this unit to separate the benzene and toluene from the reformate splitter overhead stream. However, plants without a reformate splitter may extract all the aromatics from the reformate and then split the aromatics out.
Benzene column - A simple distillation column that separates and extracted aromatics stream into benzene and a mixture of heavier aromatics. Benzene is the overhead stream and mixed heavier aromatics are the bottoms.
Toluene column - Separates Toluene from heavier aromatics in an extracted aromatics stream that has had benzene already removed. This is done with simple distillation with Toluene as the overhead stream and mixed heavier aromatics are the bottoms.
TDP (Tatoray) - A fixed bed catalytic process that converts toluene to a mix of benzene and mixed xylenes. C9-C10 can also be fed to the unit and will yield a higher concentration of xylenes.
Xylene column - Separates xylene from heavier aromatics using simple distillation. Feed is either an extracted aromatics stream that has had benzene and toluene already removed, or the bottoms from a reformate splitter. Mixed xylenes form the overhead stream and mixed heavier aromatics are the bottoms.
P-xylene extraction (Parex) - An adsorption separation used to extract p-xylene from mixed xylenes coming from the reformate splitter, the xylene column, and/or the tatoray unit. p-xylene is adsorbed and the remaining mixture of xylenes and ethylbenzene is sent to the isomar unit.
Xylene isomerization (Isomar) - An isomerization unit that takes a mix of xylenes (ethylbenzene) and converts it to molar equilibrium mix of all isomers. It is used in conjuntion with the parex unit to convert mixed xylenes and ethylbenzene to p-xylene.
The profitability of an aromatics plant depend on the premium that purified benzene and p-xylene have over there gasoline blend value of the reformate used to make them. This is largely driven by the supply of these products relative to the demand from them as feedstocks into the various polymer value chains that use them as a feed stock.