Catalytic Cracking Properties of Cross-Linked Montmorillonite (CLM) Molecular Sieves

摘要

This thesis was concerned with a systematic study of the catalytic cracking properties of corss-linked montmorillonite (CLM) molecular sieves in comparison with those of a conventional molecular sieve catalyst, i.e., CeY-type zeolite. The relative cracking yields obtained with each catalyst were determined as a function of the critical molecular dimensions of the feed using model compounds. For alkylbenzene feeds with a molecular diameter of < 9 A., i.e., cumene (6.8 A), t-butylbenzene (6.8 A), and m-diisopropylbenzene (7.9 A), intrasorption was allowed in both catalysts and consequently, the relative conversions were similar (C/sub rel/ = 0.8 to 1.2). For feeds with a molecular diameter > 9 A, intrasorption into CeY-type zeolite was either restricted or excluded, while it was fully allowed in the larger pore CLM catalysts. Consequently, relative conversions were sharply higher in favor of the CLM systems (C/sub rel/ = 1.1 to 8). Partially cross-linked montmorillonites with predominant critical pore size of 15 to 19 A, cause higher relative conversions for such large molecules than fully cross-linked montmorillonites. Penetration of tricyclodecane (d/sub min/ = 8.1 A) can occur in the intracrystalline pore systems of both catalysts. As a result, no large differences in cracking yields were found with CLM and CeY-type zeolite catalysts. On the other hand, the relative extent of cracking of dodecahydrotriphenylene with CLM (1.6) catalyst was several orders of magnitude greater than that found with the CeY catalyst. Because of its large critical diameter (12.1 A), the intrasorption of this compound into CeY was sterically excluded while it was fully allowed in the larger pore CLM catalysts. This indicates a great potential future use of DLM catalysts for cracking of heavy oils, which consist primarily of molecular components having critical diameters > 9 A. (ERA citation 10:012265)