Published October 1967
Benzene, toluene, and xylenes are coproduced and are commonly called BTX aromatics. For more than a decade they have been, and still are, in a rapid growth phase. Benzene is the second largest volume petrochemical. These factors made this technical and economic study of the BTX aromatics in the Process Economics Program desirable. This report presents the results of a study in depth of worldwide literature and process designs based on nonproprietary information.
This study recognizes some limitations of scope, because the diversity of sources and processes for BTX makes complete coverage impractical. The study is limited to recovery from petroleum sources and to dealkylation of toluene. The actual production of aromatics in catalytic reforming or other processes, being based on well-developed technology, is excluded. The separation of C8 isomers is the subject of a separate report (PEP Report No. 25).
The dominant recovery process is Shell sulfolane extraction, which is replacing Udex extraction. A design that follows actual practice closely (with the addition of a patented improvement) is given. The Lurgi Arosolvan process is being used in some new installations, but the latest version with a mixed solvent (N-methylpyrrolidone and ethylene glycol, called NMP/EG) has not yet been applied. A design is given for this mixed solvent, but the design departs from the Lurgi proposal in some respects to make it comparable with the sulfolane design. In addition, information on the Arosolvan process as designed by Lurgi is presented. The IFP process, DMSO (dimethylsulfoxide) extraction, is discussed but not designed. A design for the new Formex process of SNAM is also presented.
In this report, Section 4 studies the chemistry of dealkylation. Section 5 reviews and gives reasons for deciding among potential processes as well as those selected for evaluation. Sections 6 through 9 are devoted to individual processes. Correlations of basic data given in Appendix B may be useful in the study of these solvents applied to other feedstocks.
Nonproprietary process information was supplied by Shell Development Co., Universal Oil Products, Lurgi Gesellschaft fur Mineraloetechnik, and Snamprogetti S.p.A. Solvent stability information on DMSO was supplied by Crown Zellerbach Corporation. This assistance is gratefully acknowledged.
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