Published: February 1997
BTX aromatics (benzene, toluene and xylenes) are major fundamental building blocks for a large segment of the petrochemical industry. The largest-volume aromatics are benzene and para-xylene. World BTX demand is enjoying sustained growth of 4-7% per year, with para-xylene leading the way.
BTX aromatics are obtained mainly by extraction from catalytic reformate and pyrolysis gasoline. Toluene disproportionation (TDP) and hydrodealkylation (HDA) processes provide a swing supply of benzene and xylenes. The gasoline pool competes with BTX chemical uses, because aromatics are a major contributor to pool octane. In some regions, the phase-out of lead from gasoline is increasing the role of aromatics in gasoline. But several countries worldwide are following the U.S. lead in moving toward gasoline that is low in benzene and other aromatics. As a result, some refiners will extract additional benzene from the gasoline pool for the chemical market (ultimately at the expense of high-cost benzene production by HDA).
In this report, we evaluate the state-of-the-art technological developments in aromatics recovery via liquid extraction and extractive distillation. We also evaluate the technology and economics for Mobil's new para-xylene-selective TDP process and for conventional high-activity TDP. Results show that the para-xylene-selective technology is highly profitable, whereas the economics for the conventional TDP process are typically marginal.