Aromatic hydrocarbons—primarily benzene, toluene, and xylene (BTX)—provide the building blocks for a range of petrochemical products that are used in a wide variety of applications. In this Review, we focus on the ways in which hydrocarbon streams found in crude oil can be converted to valuable aromatic products. Most commonly, high aromatic yields within a refinery begin with the catalytic reformer, which converts gasoline-range material into a reformate stream that has a high BTX composition. While the reformer is most commonly used to boost the octane of gasoline streams, design and operational changes can lead to reformate streams with a high concentration of BTX, which can then be sent to an aromatics complex to undergo additional processing and product recovery.Refineries can capitalize on the continually growing aromatics market by integrating traditional refining units with petrochemical units in order to expand a facility's product slate and ultimately boost margins. This is achieved by effectively boosting the BTX composition of product streams from FCCUs and hydrocracking units, as well as producing suitable feedstocks for the catalytic reformer so it can smoothly and efficiently produce BTX. From there the installation of an aromatics production complex that either converts certain aromatics to more valuable ones, or recovers valuable products from mixed streams is needed, should direct feed to a nearby petrochemical complex not be feasible. These reactions include hydrodealkylation units that remove alkyl groups from heavy aromatics, disproportionation/transalkylation units the convert toluene into benzene and xylene, and isomerization units that convert less valuable meta- and ortho-xylene into highly sought after paraxylene.
Once produced, the recovery of product is equally important within the aromatics complex. Extractive distillation and fractionation can recover BTX products from mixed hydrocarbon streams, while adsorption and crystallization units often work in conjunction with isomerization units in order to recover paraxylene from mixed C8 streams. The aromatics production section also features the latest trends and technology offerings, including:
- Updated market information on aromatics supply and demand;
- Axens Aromizing process for aromatics through catalytic reforming, which was used in the world's first crude-to-paraxylene plant;
- Sinopec's FDFCC process which uses dual-rising catalytic cracking in order to boost petrochemical yields;
- The ATA-21 catalyst from Zeolyst that improves upon activity for transalkylation reactions;
- Green Chem's DTL process for converting FCC offgas into aromatics and other products;
- GT-TolAlk from GTC Technology that is used for toluene alkylation to produce paraxylene;
- IFP and Zeolyst's OparisPlus and Zotaris catalysts used for isomerization of C8 aromatics to paraxylene;
- GTC Technology's GT-BTX Plus which is capable of recovering thiophenic sulfur species in addition to BTX via extraction distillation;
- Zeolyst's and Shell's line of distillation column hardware including HiFi trays and MVG valves for optimal vapor-liquid contact and high tray efficiency; and
- A discussion of the latest patent applications and research papers regarding aromatics production technology, including a reforming unit aimed to increase PX yield that uses a riser regenerator; a method to upgrade diesel to gasoline with over 40% BTX content; methods in which to integrate traditional refining units with the aromatics complex; innovative methods in which to produce aromatics through transalkylation reactions; use of parallel liquid and gas phase isomerization reactions; utilization of both crystallization and adsorption for paraxylene recovery; the use of a dividing wall column within an aromatics complex; and more.