Abstract
Background: Examples of alternate dynamics phenomenon observed in zeolites were listed. A special attention was paid to coke alternate dynamics phenomena in deactivated HZSM5 zeolite catalysts and shortcomings of its interpretation. Present investigation deals with a coke movement of different vectors observed in deactivated catalysts based on X faujasite.
Methods: Two catalysts on the base of X zeolite by means of isomorphic partial substitution of aluminium atoms for silicon and ion exchange were synthesized. Catalysts were deactivated in isobutane with butenes alkylation in flow-circulating system and then were divided into three (catalyst 1) and two (catalyst 2) portions, which were aged for different time. Coke on samples obtained was subjected to investigation by the method of discrete-successive coke microoxidation.
Results: Dynamics of coke microoxidation in the samples of catalysts was obtained. Differences in such dynamics for variously aged samples were treated as indicating the alternate movement of coke in zeolite structure.
Conclusion: The interpretation of the nature of observed coke alternate movement was proposed. It bases on being of coke on the external surface of zeolite crystals by turn as continuous layer, which fully envelop the crystals, and as separate clusters. These states differ in chemical potential. Such difference is considered as the driving force of coke transformation from one form to another and thus a coke alternate movement in catalysts deactivated.
Keywords: Chemical potential, Clusters, Coke, Coke alternate dynamics, Disperse particles, Zeolite catalysts deactivated.
Graphical Abstract
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