Pertko O. Modification of zeolite external surface as a factor influencing the deactivation of a basic catalyst and the selectivity in hydrocarbon conversions

Zeolite catalysts of basic and acid type with modified external surface. Elucidation of the nature of FAU basic zeolite deactivation in the alkylation of toluene with methanol by expanding ideas about their interaction on the catalyst, establishing the effect of modification of the external surface of FAU and MFI zeolite microcrystals of acid and basic types on activity and selectivity in transformations of hydrocarbon. Catalyst synthesis, catalytic tests, gas chromatography, low temperature nitrogen ads./desorption, discrete-successive coke microoxidation, derivatography, X-ray fluorescence spectroscopy, NMR spectroscopy, IR spectroscopy. It has been shown for the first time that modification of the external surface of zeolite crystallites with dealuminating agents contributes to prolongation of the stable work of FAU zeolite catalysts in the cracking reaction, as well as in side-chain toluene methylation with inhibition of xylene formation in this reaction. An effective tamponing agent was found, the use of which in the modification of zeolite MFI with ammonium hexafluorosilicate led to an increase in its para-selectivity in the toluene disproportionation. The decisive role of coke in the deactivation of the toluene methylation basic catalyst, which does not contain BAS, was revealed, and the mechanism of its formation on such a catalyst was proposed. A negative role of the external surface active sites in the deactivation has been established, and modification with ammonium hexafluorosilicate has been proposed for the first time to reduce the external surface coke formation