Comparative study of n-pentane isomerization over solid acid catalysts heteropolyacid sulfated zirconia and mordenite dependence on hydrogen and platinum addition

摘要

Skeletal isomerizationof pentane over solid acid catalysts (NH_4)_2.5H_0.5PW_12O_40 sulfated zirconia and H-mordenite has been studied Hybrid bifunctional catalysts obtained by grinding equal weights of Pt/SiO_2 and each of the above solid acids were also used for the reaction Various mechanistic aspects for n-pentane isomerization over monofunctional and bifunctional catalysts in the presence or absence of hydrogen in the feed are siscussed Analysis of product distributions at 423 and 473 K indicated that over monofunctional heteropolyacids and sulfated zirconia catalysts the main reaction path is the bimolecular one involving conjunct polymerization and cracking Under these operation conditions the selectivity to isopentane is low monofunctional H-mordenite shows a significant activity only at 498 K HPA and ZrO_2-SO_4 although showing stronger acidity than H-mordenite do not activate n-pentane through a monomolecular pathas "superacid-type catalysts" are expected to Bifunctional isomerization of pentane appears at a reaction temperature of 473 K and up since the equilibrium concentration of pentene is signifiant only when the reactin temperature is 473 K and up A monomolecular bifunctional mechanism is the preferred route for reaching high isomerization selectivity.