Xylenes and Ethylbenzene

AbstractThis article reviews the properties, commercial manufacturing aspects, and uses of the three xylene isomers, ie,o‐xylene,m‐xylene, andp‐xylene, and the ethylbenzene present in mixed xylene streams. Chemical reactions discussed are migration of the alkyl groups, including 1,2 intramolecular shifts and transalkylation; reactions of the alkyl groups, including oxidation, polycondensation, and ammoxidation; reactions of the aromatic ring; and complex formation. Aspects of commercial manufacture that are covered include initial production of mixed xylenes; separation processes used to produce high purityp‐xylene,o‐xylene, andm‐xylene; and xylene isomerization processes. Catalytic reforming and toluene disproportionation/transalkylation are the primary mixed xylene production routes discussed. The xylene isomer separation processes of crystallization, adsorption, and complex formation are described. The commercially important xylene isomerization processes are reviewed. Worldwide production data for the three xylene isomers and ethylbenzene are presented along with a list of the U.S. producers and their production capacities. Analytical techniques and important health and safety factors are also summarized.