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Abstract
Noble metal supported zeolite isomerization catalysts are widely used in chemical industry. Recently, considerable attention has been paid to the question of maximum metal phase dispersion, while localization and uniformity of the distribution of metal particles on the support are often not taken into account. The last significantly affects on the activity and selectivity of the catalysts. The aim of this work was to assess the effect of the sequence of synthesis stages of palladiumcontaining MFI zeolites (synthesis of the acid form and metal reduction) on the size of metal particles and their localization, as well as the activity/selectivity of the catalysts in isomerization of nhexane. A number of palladium-containing catalysts based on HMFI and NH4MFI with a metal component content from 0.1 to 1.0 wt. % has been synthesized by impregnation. The study of samples by nitrogen low-temperature adsorption/desorption method showed a weak effect of palladium modification on the texture characteristics of the samples. It was found using transmission electron microscopy that the particle size of palladium increases with increase in amount of metal deposited. For almost all samples nanosized palladium particles have been recorded. The samples with palladium deposited on the hydrogen form of pentasil in the amount of 0.5 and 1.0 wt. % turned out to be the most active and most selective, however, no unequivocal dependence of the catalyst efficiency on the size of the metal particles was found.
References
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