Aromatics Industry
Aromatics are a special class of molecules because they have the equivalent of 1.5 bonds between each carbon atom. Sometimes they are drawn with alternating double bonds but in reality, (according to molecular quantum modelling), the electrons in the aromatic rings are delocalised. This means that the charge density is shared equally amongst all the carbon atoms. This is why you will often see aromatics drawn as a cyclic six-membered ring containing a circle.
Building block chemicals in this class are: benzene, toluene, ethylbenzene and xylenes (BTEX). They arise from distillation, extraction, reforming, cracking and specialised upgrading routes across the hydrocarbon value chains. Much benzene supply is derived not from standalone units, but as mixtures with other aromatics, or as byproducts of separate industries such as coal processing.
Meanwhile, xylenes are actually a group of three structural isomers each with the same formula (C8H10). However one of those three isomers “paraxylene” (PX) has a much higher maket value than the others. This is because it is one of the two main monomers used to produce polyethylene terephthalate (PET) – a type of polyester widely used in disposable soda and water bottles. PET is also widely chosen for textile fibres used in clothing.
The remaining two xylenes – ortho-xylene and meta-xylene – together referred to as “mixed xylenes” are often blended into gasoline rather than being sold for chemical production. This is a much lower value application compared to PX for PET, and the aromatics section in a modern refinery can be tuned to boost the PX yield by performing carbon rearrangement reactions on the other aromatics.
Mixed xylenes are nonetheless important fuel components, as they can be blended in to gasoline at up to 35-40 vol% of the total gasoline pool. This help refiners to achieve required gasoline quality specifications and scale because mixed xylenes have a good octane rating and high purity with regards to sulphur.
As with olefins and feedstocks, aromatics can be derived from fossil sources, biobased feeds and recyclate. In fact the recycled or biobased content in a plastic soda bottle is derived largely from the PX portion of the base PET polymer resin. If you spend time in the Hexavault Knowledge Rooms below – see if you can spot the explanation for the difference between a polymer and a plastic!
Aromatics – Hexavault Knowledge Rooms
Benzene – Market Profile
Toluene – Market Profile
Paraxylene – Market Profile
Orthoxylene – Market Profile
Metaxylene – Market Profile
Ethylbenzene – Market Profile
Styrene – Market Profile
Aromatics – Refinery
Aromatics – Coal
Aromatics – Biobased
Aromatics – Other