Catalysis by crystalline aluminosilicates I. Cracking of hydrocarbon types over sodium and calcium “X” zeolites

• Published in: Journal of catalysis 1962-08, Vol.1 (4), p.301-306
• Main Authors: Frilette, V.J., Weisz, P.B., Golden, R.L.
• Format: Article
• Language: English
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/0021-9517(62)90057-X

Crystalline sodium aluminosilicates of the three-dimensional rigid-framework type (molecular sieves) exhibit unexpected catalytic activity for cracking various hydrocarbons. The sodium “X” crystals exhibit very high activity with paraffin and olefin hydrocarbons. Paraffin cracking activity exceeds that of conventional silica-alumina cracking catalyst. The products formed are virtually free of branched chain hydrocarbons. In contrast to the conventional cracking catalyst, this salt is ineffective as a catalyst for the dealkylation of cumene. Replacing the sodium by the calcium ion radically alters the catalytic properties of the solid. The calcium salt, even more active than the sodium form for paraffin or olefin cracking, produces considerable amounts of branched chain hydrocarbons. Furthermore, it is a highly active catalyst for the dealkylation of cumene. The relative activity toward various hydrocarbons, and the nature of the products from this salt form approach that of silica-alumina. Available evidence indicates that the catalytic centers are located within the interstitial spaces of the dehydrated crystals. Change of the mobile cation from calcium to sodium in the same crystal changes its role from that of an acid catalyst to one which intervenes in a radical mechanism.