n-Hexane Isomerisation: Exploit Hydrogen Spillover to Reduce Catalyst Costs

Abstract

We report the role of hydrogen spillover in n-hexane isomerisation over carbon nanotubes or SiC mixed with hierarchical zeolite beta. Here we infer that: (1) hydrogen spillover is a necessary step; (2) spilled-over H hydrogenates isomerised olefin at Brønsted acid sites only; and (3) closeness between acid and metal sites at the nanoscale enhances the rate of reaction, though this is not a requirement for this reaction to proceed. The economic advantage of the spillover phenomenon (necessitating less Pt on the catalyst) has been highlighted.

Combined influence of alkaline earth metals and CO2 on performance of hierarchical zeolite Beta in n-hexane isomerization

“…Pt was introduced into desilicated H-Beta by incipient wetness impregnation (IWI) method and this was followed by depositing an alkaline earth metal adopting the same IWI method [1]. Pt content of each catalyst was 0.5 wt % and the metal content was 3 wt %.…”

“…n-Alkane dehydrogenates to corresponding olefin which diffuses to acid sites in the neighborhood. At acid sites, olefin converts structurally and upon reaching the metal site it saturates to branched paraffin, though a little variation in this conventional mechanism has also been proposed [1]. The metal function needed on the acidic catalyst has been widely reported to be imparted by Pt.…”

“…Among the probable candidates, keeping hydrothermal stability of the catalyst in mind, zeolites Beta has remained the catalyst of choice. Readers are referred to relatively recent works [1,2] for introduction to paraffin isomerization and review articles by Valavarasu and Sairam [3], and Akhmedov et al [4] for details and comprehensive intricacies of various commercial processes. Now, when the molecular size of product increases as a result of the reaction, it is worth expecting that (a) smaller crystal size, preferably in nanometer size affording smaller diffusion length and enhanced external surface area and (b) generation of mesoporosity in zeolites crystals would be beneficial for the reaction.…”