Dehydrocyclization—Heterogeneous

Abstract

The formation of aromatic rings from alkanes such as hexane, heptane, octane, and so on (aromatization or dehydrocyclization) on oxide catalysts: chromia, lanthana, metals, such as platinum, palladium, and so on, and nonacidic (Na‐ or Ba‐L zeolite) supports is a “monofunctional” route, catalyzed by the active ingredient itself. A bifunctional route prevails in naphtha reforming (platforming) over Pt on acidic supports (eg, alumina). Interactions of Pt with acidic or alkaline support can be important for aromatization. The metallic function can also catalyze the formation of five‐membered ring(s): C5‐cyclization. The effect of added metallic components resulting in bimetallic catalysts (such as PtRe, PtSn, and so on) as well as the effect of nonmetallic components (Cl, S, C, H) is discussed. Aromatization requiring skeletal rearrangement (eg, of alkylpentane feeds) can also take place. Cyclic hydrocarbons may undergo ring enlargement and ring contraction. The same catalyst may promote the formation of a second ring in alkylcyclopentanes. The buildup of aromatic rings is also possible from smaller molecules (ethane, propane, butane) by dehydrocyclodimerization over bifunctional catalysts, such as ZSM 5 zeolites containing Pt, Zn, but first of all Ga (eg, in the CYCLAR process). Aromatics can be produced even from methane (Mo carbide‐ZSM‐5 or Pd‐Co catalysts).

A magyar sajtópolitika a koalíciós időszakban (1944–1949)

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