Abstract: In order to optimize the product structure of a refinery, the xylene unit was modified with the adaptability of changing catalyst, and the isomerization route was changed from ethylbenzene conversion type to de-ethylation type. While reducing the loss of aromatics, the source of aromatics could be maximized by converting them into p-xylene and benzene, thus increasing the utilization ratio of aromatics. At the same time, ethane-rich by-product gas was recovered as high value-added ethylene feedstock to achieve maximum benefits. The transformation strategy included the optimization of catalyst function, process flow adjustment and thermal integration，which could provide some reference for the transformation of similar units.

Key words: unit modification, catalyst, thermal integration, aromatic hydrocarbon resources, p-xylene, ethane-rich gas