I would like to ask about the requirements for xylene as a raw material in PX plants

There are many methods for extracting p-xylene from mixed xylene, such as sulfonation, eutectic method, cryogenic crystallization, and adsorption separation. Among them, the adsorption separation method has become the most widely used method for PX production at present due to its simple process, high product purity, and high yield. The main patented technologies include UOP’s Parex technology and Axens’ Eluxyl technology. Currently, there are many manufacturers using UOP technology, while fewer use Axens technology; however, due to technical advantages such as its ease of implementation on a larger scale, it has also seen rapid adoption in recent years. China National Offshore Oil Corporation’s 840,000-ton/year PX plant in Huizhou and Dalian Fujia’s 900,000-ton/year PX plant both utilize Axens technology. Each of the two technologies has its advantages and disadvantages. The requirement for raw materials mentioned by the poster is that the PX content in mixed xylene must not be lower than 23%, and the bromine index must be less than 20.

The quality requirements for the raw materials include a benzene content of less than 500 PPm, as well as limits on C9 aromatics, olefins (bromine index), metals, and water content. For xylene, it is sufficient to ensure it is in a balanced state during casting; the ethylbenzene level should not be too high, otherwise the PX product will not meet the standards, but this will not affect the adsorbent