N-Hexane Isomerization on Ni-Pt/Catalysts Supported on Mordenite

Geovana S V Martins,Carlos M N Yoshioka,Gina Pecchi,Meiry G F Rodrigues,Dilson Cardoso,Everton R F Dos Santos

doi:10.4236/mrc.2013.24017

Abstract

The aim of this work was to evaluate the catalytic properties for n-hexane isomerization of bifunctional monometallic (Ni or Pt) and bimetallic catalysts (Pt-Ni), using HMOR zeolite as support. The method used for metal dispersion in the zeolite was competitive ion exchange using ammine complexes [Ni(NH3)6]Cl2 and [Pt(NH3)4]Cl2 as precursors. The catalysts were characterized by X-Ray diffraction, X-Ray energy dispersion spectroscopy, temperature-programmed reduction and transmission electron microscopy. The n-hexane isomerization reaction using the catalysts was carried out to evaluate the catalyst activity. The reaction was carried out in a fixed bed reactor operating at 250?C, 1 atm, H2/C6 = 9 molar ratio. The profiles obtained from TPR suggest that, for bimetallic catalysts, the presence of platinum facilitates the reduction of Ni2+ cations. The bimetallic catalysts presented a higher activity in the isomerization of n-hexane when compared to the monometallic ones, as well better stability as the Pt content in the solid increases.

Highlights

IntroductionOne of the key specifications of gasoline is the octane number, which corresponds to the fuel knocking (self-igniting) property in internal combustion engine
The profiles obtained from Temperature Programmed Reduction (TPR) suggest that, for bimetallic catalysts, the presence of platinum facilitates the reduction of Ni2+ cations
The bimetallic catalysts presented a higher activity in the isomerization of n-hexane when compared to the monometallic ones, as well better stability as the Pt content in the solid increases

Summary

Introduction

One of the key specifications of gasoline is the octane number, which corresponds to the fuel knocking (self-igniting) property in internal combustion engine. High octane numbers correlate to a low knocking intensity that is related to good engine performance [1]. Branched paraffins have higher octane numbers than corresponding linear paraffins. Linear hexane has an octane number equal to 25, while 2,2-dimethylbutane, an hexane isomer, has an octane number equal to 92. Isomerization of linear paraffins, a process in which straight-chain hydrocarbon molecules rearrange to form branched hydrocarbons, is used to improve gasoline quality [2]

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