DEHYDROCYCLODIMERIZATION

This review describes dehydrocyclodimerization, the conversion of light (C3-C5) paraffins or olefins to aromatics. The product aromatics always contain more carbon atoms than the reactants. The reaction is carried out above 430 °C in the absence of added hydrogen over dual function catalysts containing acidic and dehydrogenation components. Operation is cyclic: dehydrocyclodimerization and regeneration cycles follow each other. Xylenes, ethylbenzene, toluene, and benzene are the major aromatics produced from butanes. Pentane reactants give some bicyclic aromatics in addition. The principal product of propane dehydrocyclodimerization is benzene. Ethane and ethylene yield mostly benzene in dehydrocyclotrimerization, a related reaction. Catalysts are platinum and platinum group metals on alumina, or oxides of Cr, Mo, V, and W on alumina. Best results (>30% ultimate recycle aromatic yields) are obtained over physical mixtures of a neutral dehydrogenation component with acidic alumina. The review briefly covers oxidative dehydrocyclodimerization also. © 1979, American Chemical Society. All rights reserved.