Impact of Chain Length on the Catalytic Performance in Hydroisomerization of n-Alkanes Over Commercial and Alkaline Treated *BEA Zeolites
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The present paper highlights the influence of desilication of nanocrystal *BEA zeolites (CP811 and CP814E) by different alkaline treatments in presence of NaOH alone, NaOH + TPABr and NaOH + TBAOH, on the catalytic performance in the hydroisomerization reactions of n-alkanes (n-C10, n-C12 and n-C14). The well-balanced catalyst was reached after impregnation of 1.5 wt% of Pt, where the activity and isomers selectivity was seen to be the maximum, knowing that the Pt content effect was studied on the CP811 zeolite catalyst. All the other catalysts were after impregnated by approximately 1.5 wt% of Pt. The improvement of the textural properties by means of desilication was not always accounting for the influence of the catalytic performance of the catalysts, but rather it may be the bifunctional characteristics in charge. The impact of chain length was investigated on the catalysts to study if the presence of the inter- and intracrystalline mesopores would account for better diffusion of larger molecules as, n-C12 and n-C14. It was found on the majority of the catalysts that the activity was high whether the chain length was, but the isomers selectivity was decreasing with chain length except on one catalyst that possesses high textural and bifunctional characteristics. Among the three n-alkanes studied, n-C12 have marked the highest TOF values and lowest selectivity to isomers, a phenomenon attributed to the confinement effect that seems to increase the interaction of n-C12 molecules with the acidic sites of the zeolites, apparently causing their strength to be higher. This effect was pronounced more with n-C12 than the other two n-alkanes.
Keywords*BEA zeolite Desilication Bifunctional characteristics Hydroisomerization Confinement effect
Thanks for the “Islamic Association for Guidance and Higher Education” present in Lebanon, for its financial support.
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